diff --git a/CompileTests/MultiModule/Sources/ImportsAPublicly/imports_a_publicly.pb.swift b/CompileTests/MultiModule/Sources/ImportsAPublicly/imports_a_publicly.pb.swift
index 556b2ed19..99f4f3e88 100644
--- a/CompileTests/MultiModule/Sources/ImportsAPublicly/imports_a_publicly.pb.swift
+++ b/CompileTests/MultiModule/Sources/ImportsAPublicly/imports_a_publicly.pb.swift
@@ -10,7 +10,10 @@
 import Foundation
 import SwiftProtobuf
 
-import ModuleA
+// Use of 'import public' causes re-exports:
+@_exported import enum ModuleA.E
+@_exported import let ModuleA.Extensions_ext_str
+@_exported import struct ModuleA.A
 
 // If the compiler emits an error on this type, it is because this file
 // was generated by a version of the `protoc` Swift plug-in that is
@@ -62,6 +65,11 @@ extension ImportsAPublicly: SwiftProtobuf.Message, SwiftProtobuf._MessageImpleme
     12: .same(proto: "e"),
   ]
 
+  public var isInitialized: Bool {
+    if let v = self._a, !v.isInitialized {return false}
+    return true
+  }
+
   public mutating func decodeMessage<D: SwiftProtobuf.Decoder>(decoder: inout D) throws {
     while let fieldNumber = try decoder.nextFieldNumber() {
       // The use of inline closures is to circumvent an issue where the compiler
diff --git a/CompileTests/MultiModule/Sources/ImportsImportsAPublicly/imports_imports_a_publicly.pb.swift b/CompileTests/MultiModule/Sources/ImportsImportsAPublicly/imports_imports_a_publicly.pb.swift
index 8a345f5d0..7e1ec8739 100644
--- a/CompileTests/MultiModule/Sources/ImportsImportsAPublicly/imports_imports_a_publicly.pb.swift
+++ b/CompileTests/MultiModule/Sources/ImportsImportsAPublicly/imports_imports_a_publicly.pb.swift
@@ -10,8 +10,11 @@
 import Foundation
 import SwiftProtobuf
 
-import ImportsAPublicly
-import ModuleA
+// Use of 'import public' causes re-exports:
+@_exported import enum ModuleA.E
+@_exported import let ModuleA.Extensions_ext_str
+@_exported import struct ImportsAPublicly.ImportsAPublicly
+@_exported import struct ModuleA.A
 
 // If the compiler emits an error on this type, it is because this file
 // was generated by a version of the `protoc` Swift plug-in that is
@@ -63,6 +66,11 @@ extension ImportsImportsAPublicly: SwiftProtobuf.Message, SwiftProtobuf._Message
     22: .same(proto: "e"),
   ]
 
+  public var isInitialized: Bool {
+    if let v = self._a, !v.isInitialized {return false}
+    return true
+  }
+
   public mutating func decodeMessage<D: SwiftProtobuf.Decoder>(decoder: inout D) throws {
     while let fieldNumber = try decoder.nextFieldNumber() {
       // The use of inline closures is to circumvent an issue where the compiler
diff --git a/CompileTests/MultiModule/Sources/ModuleA/a.pb.swift b/CompileTests/MultiModule/Sources/ModuleA/a.pb.swift
index e456acc57..165a10475 100644
--- a/CompileTests/MultiModule/Sources/ModuleA/a.pb.swift
+++ b/CompileTests/MultiModule/Sources/ModuleA/a.pb.swift
@@ -49,7 +49,7 @@ public enum E: SwiftProtobuf.Enum {
 
 }
 
-public struct A: Sendable {
+public struct A: SwiftProtobuf.ExtensibleMessage, Sendable {
   // SwiftProtobuf.Message conformance is added in an extension below. See the
   // `Message` and `Message+*Additions` files in the SwiftProtobuf library for
   // methods supported on all messages.
@@ -67,9 +67,57 @@ public struct A: Sendable {
 
   public init() {}
 
+  public var _protobuf_extensionFieldValues = SwiftProtobuf.ExtensionFieldValueSet()
   fileprivate var _e: E? = nil
 }
 
+// MARK: - Extension support defined in a.proto.
+
+// MARK: - Extension Properties
+
+// Swift Extensions on the exteneded Messages to add easy access to the declared
+// extension fields. The names are based on the extension field name from the proto
+// declaration. To avoid naming collisions, the names are prefixed with the name of
+// the scope where the extend directive occurs.
+
+extension A {
+
+  public var extStr: String {
+    get {return getExtensionValue(ext: Extensions_ext_str) ?? String()}
+    set {setExtensionValue(ext: Extensions_ext_str, value: newValue)}
+  }
+  /// Returns true if extension `Extensions_ext_str`
+  /// has been explicitly set.
+  public var hasExtStr: Bool {
+    return hasExtensionValue(ext: Extensions_ext_str)
+  }
+  /// Clears the value of extension `Extensions_ext_str`.
+  /// Subsequent reads from it will return its default value.
+  public mutating func clearExtStr() {
+    clearExtensionValue(ext: Extensions_ext_str)
+  }
+
+}
+
+// MARK: - File's ExtensionMap: A_Extensions
+
+/// A `SwiftProtobuf.SimpleExtensionMap` that includes all of the extensions defined by
+/// this .proto file. It can be used any place an `SwiftProtobuf.ExtensionMap` is needed
+/// in parsing, or it can be combined with other `SwiftProtobuf.SimpleExtensionMap`s to create
+/// a larger `SwiftProtobuf.SimpleExtensionMap`.
+public let A_Extensions: SwiftProtobuf.SimpleExtensionMap = [
+  Extensions_ext_str
+]
+
+// Extension Objects - The only reason these might be needed is when manually
+// constructing a `SimpleExtensionMap`, otherwise, use the above _Extension Properties_
+// accessors for the extension fields on the messages directly.
+
+public let Extensions_ext_str = SwiftProtobuf.MessageExtension<SwiftProtobuf.OptionalExtensionField<SwiftProtobuf.ProtobufString>, A>(
+  _protobuf_fieldNumber: 100,
+  fieldName: "ext_str"
+)
+
 // MARK: - Code below here is support for the SwiftProtobuf runtime.
 
 extension E: SwiftProtobuf._ProtoNameProviding {
@@ -86,6 +134,11 @@ extension A: SwiftProtobuf.Message, SwiftProtobuf._MessageImplementationBase, Sw
     1: .same(proto: "e"),
   ]
 
+  public var isInitialized: Bool {
+    if !_protobuf_extensionFieldValues.isInitialized {return false}
+    return true
+  }
+
   public mutating func decodeMessage<D: SwiftProtobuf.Decoder>(decoder: inout D) throws {
     while let fieldNumber = try decoder.nextFieldNumber() {
       // The use of inline closures is to circumvent an issue where the compiler
@@ -93,6 +146,8 @@ extension A: SwiftProtobuf.Message, SwiftProtobuf._MessageImplementationBase, Sw
       // enabled. https://github.com/apple/swift-protobuf/issues/1034
       switch fieldNumber {
       case 1: try { try decoder.decodeSingularEnumField(value: &self._e) }()
+      case 100..<1001:
+        try { try decoder.decodeExtensionField(values: &_protobuf_extensionFieldValues, messageType: A.self, fieldNumber: fieldNumber) }()
       default: break
       }
     }
@@ -106,12 +161,14 @@ extension A: SwiftProtobuf.Message, SwiftProtobuf._MessageImplementationBase, Sw
     try { if let v = self._e {
       try visitor.visitSingularEnumField(value: v, fieldNumber: 1)
     } }()
+    try visitor.visitExtensionFields(fields: _protobuf_extensionFieldValues, start: 100, end: 1001)
     try unknownFields.traverse(visitor: &visitor)
   }
 
   public static func ==(lhs: A, rhs: A) -> Bool {
     if lhs._e != rhs._e {return false}
     if lhs.unknownFields != rhs.unknownFields {return false}
+    if lhs._protobuf_extensionFieldValues != rhs._protobuf_extensionFieldValues {return false}
     return true
   }
 }
diff --git a/CompileTests/MultiModule/Tests/Test1/test1.swift b/CompileTests/MultiModule/Tests/Test1/test1.swift
index f186277bd..474a7c09c 100644
--- a/CompileTests/MultiModule/Tests/Test1/test1.swift
+++ b/CompileTests/MultiModule/Tests/Test1/test1.swift
@@ -1,5 +1,5 @@
 import ImportsAPublicly
-import ModuleA  // Needed because `import public` doesn't help Swift
+// Don't need to import ModuleA because of the file being a `import public`
 
 import XCTest
 
diff --git a/CompileTests/MultiModule/Tests/Test1/uses_a_transitively.pb.swift b/CompileTests/MultiModule/Tests/Test1/uses_a_transitively.pb.swift
index 3bb4d6701..e88624091 100644
--- a/CompileTests/MultiModule/Tests/Test1/uses_a_transitively.pb.swift
+++ b/CompileTests/MultiModule/Tests/Test1/uses_a_transitively.pb.swift
@@ -11,7 +11,6 @@ import Foundation
 import SwiftProtobuf
 
 import ImportsAPublicly
-import ModuleA
 
 // If the compiler emits an error on this type, it is because this file
 // was generated by a version of the `protoc` Swift plug-in that is
@@ -63,6 +62,11 @@ extension UsesATransitively: SwiftProtobuf.Message, SwiftProtobuf._MessageImplem
     102: .same(proto: "e"),
   ]
 
+  public var isInitialized: Bool {
+    if let v = self._a, !v.isInitialized {return false}
+    return true
+  }
+
   public mutating func decodeMessage<D: SwiftProtobuf.Decoder>(decoder: inout D) throws {
     while let fieldNumber = try decoder.nextFieldNumber() {
       // The use of inline closures is to circumvent an issue where the compiler
diff --git a/CompileTests/MultiModule/Tests/Test2/test2.swift b/CompileTests/MultiModule/Tests/Test2/test2.swift
index e20ebd130..45d62fbb5 100644
--- a/CompileTests/MultiModule/Tests/Test2/test2.swift
+++ b/CompileTests/MultiModule/Tests/Test2/test2.swift
@@ -1,5 +1,5 @@
 import ImportsImportsAPublicly
-import ModuleA  // Needed because `import public` doesn't help Swift
+// Don't need to import ModuleA because of the file being a `import public`
 
 import XCTest
 
diff --git a/CompileTests/MultiModule/Tests/Test2/uses_a_transitively2.pb.swift b/CompileTests/MultiModule/Tests/Test2/uses_a_transitively2.pb.swift
index 7dd0c210e..6c056cb8a 100644
--- a/CompileTests/MultiModule/Tests/Test2/uses_a_transitively2.pb.swift
+++ b/CompileTests/MultiModule/Tests/Test2/uses_a_transitively2.pb.swift
@@ -10,9 +10,7 @@
 import Foundation
 import SwiftProtobuf
 
-import ImportsAPublicly
 import ImportsImportsAPublicly
-import ModuleA
 
 // If the compiler emits an error on this type, it is because this file
 // was generated by a version of the `protoc` Swift plug-in that is
@@ -64,6 +62,11 @@ extension UsesATransitively2: SwiftProtobuf.Message, SwiftProtobuf._MessageImple
     122: .same(proto: "e"),
   ]
 
+  public var isInitialized: Bool {
+    if let v = self._a, !v.isInitialized {return false}
+    return true
+  }
+
   public mutating func decodeMessage<D: SwiftProtobuf.Decoder>(decoder: inout D) throws {
     while let fieldNumber = try decoder.nextFieldNumber() {
       // The use of inline closures is to circumvent an issue where the compiler
diff --git a/Protos/CompileTests/MultiModule/Sources/ModuleA/a.proto b/Protos/CompileTests/MultiModule/Sources/ModuleA/a.proto
index 7a2ef4496..75c1506a7 100644
--- a/Protos/CompileTests/MultiModule/Sources/ModuleA/a.proto
+++ b/Protos/CompileTests/MultiModule/Sources/ModuleA/a.proto
@@ -6,4 +6,9 @@ enum E {
 
 message A {
   optional E e = 1;
+  extensions 100 to 1000;
+}
+
+extend A {
+  optional string ext_str = 100;
 }
diff --git a/Reference/CompileTests/MultiModule/Sources/ImportsAPublicly/imports_a_publicly.pb.swift b/Reference/CompileTests/MultiModule/Sources/ImportsAPublicly/imports_a_publicly.pb.swift
index 556b2ed19..99f4f3e88 100644
--- a/Reference/CompileTests/MultiModule/Sources/ImportsAPublicly/imports_a_publicly.pb.swift
+++ b/Reference/CompileTests/MultiModule/Sources/ImportsAPublicly/imports_a_publicly.pb.swift
@@ -10,7 +10,10 @@
 import Foundation
 import SwiftProtobuf
 
-import ModuleA
+// Use of 'import public' causes re-exports:
+@_exported import enum ModuleA.E
+@_exported import let ModuleA.Extensions_ext_str
+@_exported import struct ModuleA.A
 
 // If the compiler emits an error on this type, it is because this file
 // was generated by a version of the `protoc` Swift plug-in that is
@@ -62,6 +65,11 @@ extension ImportsAPublicly: SwiftProtobuf.Message, SwiftProtobuf._MessageImpleme
     12: .same(proto: "e"),
   ]
 
+  public var isInitialized: Bool {
+    if let v = self._a, !v.isInitialized {return false}
+    return true
+  }
+
   public mutating func decodeMessage<D: SwiftProtobuf.Decoder>(decoder: inout D) throws {
     while let fieldNumber = try decoder.nextFieldNumber() {
       // The use of inline closures is to circumvent an issue where the compiler
diff --git a/Reference/CompileTests/MultiModule/Sources/ImportsImportsAPublicly/imports_imports_a_publicly.pb.swift b/Reference/CompileTests/MultiModule/Sources/ImportsImportsAPublicly/imports_imports_a_publicly.pb.swift
index 8a345f5d0..7e1ec8739 100644
--- a/Reference/CompileTests/MultiModule/Sources/ImportsImportsAPublicly/imports_imports_a_publicly.pb.swift
+++ b/Reference/CompileTests/MultiModule/Sources/ImportsImportsAPublicly/imports_imports_a_publicly.pb.swift
@@ -10,8 +10,11 @@
 import Foundation
 import SwiftProtobuf
 
-import ImportsAPublicly
-import ModuleA
+// Use of 'import public' causes re-exports:
+@_exported import enum ModuleA.E
+@_exported import let ModuleA.Extensions_ext_str
+@_exported import struct ImportsAPublicly.ImportsAPublicly
+@_exported import struct ModuleA.A
 
 // If the compiler emits an error on this type, it is because this file
 // was generated by a version of the `protoc` Swift plug-in that is
@@ -63,6 +66,11 @@ extension ImportsImportsAPublicly: SwiftProtobuf.Message, SwiftProtobuf._Message
     22: .same(proto: "e"),
   ]
 
+  public var isInitialized: Bool {
+    if let v = self._a, !v.isInitialized {return false}
+    return true
+  }
+
   public mutating func decodeMessage<D: SwiftProtobuf.Decoder>(decoder: inout D) throws {
     while let fieldNumber = try decoder.nextFieldNumber() {
       // The use of inline closures is to circumvent an issue where the compiler
diff --git a/Reference/CompileTests/MultiModule/Sources/ModuleA/a.pb.swift b/Reference/CompileTests/MultiModule/Sources/ModuleA/a.pb.swift
index e456acc57..165a10475 100644
--- a/Reference/CompileTests/MultiModule/Sources/ModuleA/a.pb.swift
+++ b/Reference/CompileTests/MultiModule/Sources/ModuleA/a.pb.swift
@@ -49,7 +49,7 @@ public enum E: SwiftProtobuf.Enum {
 
 }
 
-public struct A: Sendable {
+public struct A: SwiftProtobuf.ExtensibleMessage, Sendable {
   // SwiftProtobuf.Message conformance is added in an extension below. See the
   // `Message` and `Message+*Additions` files in the SwiftProtobuf library for
   // methods supported on all messages.
@@ -67,9 +67,57 @@ public struct A: Sendable {
 
   public init() {}
 
+  public var _protobuf_extensionFieldValues = SwiftProtobuf.ExtensionFieldValueSet()
   fileprivate var _e: E? = nil
 }
 
+// MARK: - Extension support defined in a.proto.
+
+// MARK: - Extension Properties
+
+// Swift Extensions on the exteneded Messages to add easy access to the declared
+// extension fields. The names are based on the extension field name from the proto
+// declaration. To avoid naming collisions, the names are prefixed with the name of
+// the scope where the extend directive occurs.
+
+extension A {
+
+  public var extStr: String {
+    get {return getExtensionValue(ext: Extensions_ext_str) ?? String()}
+    set {setExtensionValue(ext: Extensions_ext_str, value: newValue)}
+  }
+  /// Returns true if extension `Extensions_ext_str`
+  /// has been explicitly set.
+  public var hasExtStr: Bool {
+    return hasExtensionValue(ext: Extensions_ext_str)
+  }
+  /// Clears the value of extension `Extensions_ext_str`.
+  /// Subsequent reads from it will return its default value.
+  public mutating func clearExtStr() {
+    clearExtensionValue(ext: Extensions_ext_str)
+  }
+
+}
+
+// MARK: - File's ExtensionMap: A_Extensions
+
+/// A `SwiftProtobuf.SimpleExtensionMap` that includes all of the extensions defined by
+/// this .proto file. It can be used any place an `SwiftProtobuf.ExtensionMap` is needed
+/// in parsing, or it can be combined with other `SwiftProtobuf.SimpleExtensionMap`s to create
+/// a larger `SwiftProtobuf.SimpleExtensionMap`.
+public let A_Extensions: SwiftProtobuf.SimpleExtensionMap = [
+  Extensions_ext_str
+]
+
+// Extension Objects - The only reason these might be needed is when manually
+// constructing a `SimpleExtensionMap`, otherwise, use the above _Extension Properties_
+// accessors for the extension fields on the messages directly.
+
+public let Extensions_ext_str = SwiftProtobuf.MessageExtension<SwiftProtobuf.OptionalExtensionField<SwiftProtobuf.ProtobufString>, A>(
+  _protobuf_fieldNumber: 100,
+  fieldName: "ext_str"
+)
+
 // MARK: - Code below here is support for the SwiftProtobuf runtime.
 
 extension E: SwiftProtobuf._ProtoNameProviding {
@@ -86,6 +134,11 @@ extension A: SwiftProtobuf.Message, SwiftProtobuf._MessageImplementationBase, Sw
     1: .same(proto: "e"),
   ]
 
+  public var isInitialized: Bool {
+    if !_protobuf_extensionFieldValues.isInitialized {return false}
+    return true
+  }
+
   public mutating func decodeMessage<D: SwiftProtobuf.Decoder>(decoder: inout D) throws {
     while let fieldNumber = try decoder.nextFieldNumber() {
       // The use of inline closures is to circumvent an issue where the compiler
@@ -93,6 +146,8 @@ extension A: SwiftProtobuf.Message, SwiftProtobuf._MessageImplementationBase, Sw
       // enabled. https://github.com/apple/swift-protobuf/issues/1034
       switch fieldNumber {
       case 1: try { try decoder.decodeSingularEnumField(value: &self._e) }()
+      case 100..<1001:
+        try { try decoder.decodeExtensionField(values: &_protobuf_extensionFieldValues, messageType: A.self, fieldNumber: fieldNumber) }()
       default: break
       }
     }
@@ -106,12 +161,14 @@ extension A: SwiftProtobuf.Message, SwiftProtobuf._MessageImplementationBase, Sw
     try { if let v = self._e {
       try visitor.visitSingularEnumField(value: v, fieldNumber: 1)
     } }()
+    try visitor.visitExtensionFields(fields: _protobuf_extensionFieldValues, start: 100, end: 1001)
     try unknownFields.traverse(visitor: &visitor)
   }
 
   public static func ==(lhs: A, rhs: A) -> Bool {
     if lhs._e != rhs._e {return false}
     if lhs.unknownFields != rhs.unknownFields {return false}
+    if lhs._protobuf_extensionFieldValues != rhs._protobuf_extensionFieldValues {return false}
     return true
   }
 }
diff --git a/Reference/CompileTests/MultiModule/Tests/Test1/uses_a_transitively.pb.swift b/Reference/CompileTests/MultiModule/Tests/Test1/uses_a_transitively.pb.swift
index 3bb4d6701..e88624091 100644
--- a/Reference/CompileTests/MultiModule/Tests/Test1/uses_a_transitively.pb.swift
+++ b/Reference/CompileTests/MultiModule/Tests/Test1/uses_a_transitively.pb.swift
@@ -11,7 +11,6 @@ import Foundation
 import SwiftProtobuf
 
 import ImportsAPublicly
-import ModuleA
 
 // If the compiler emits an error on this type, it is because this file
 // was generated by a version of the `protoc` Swift plug-in that is
@@ -63,6 +62,11 @@ extension UsesATransitively: SwiftProtobuf.Message, SwiftProtobuf._MessageImplem
     102: .same(proto: "e"),
   ]
 
+  public var isInitialized: Bool {
+    if let v = self._a, !v.isInitialized {return false}
+    return true
+  }
+
   public mutating func decodeMessage<D: SwiftProtobuf.Decoder>(decoder: inout D) throws {
     while let fieldNumber = try decoder.nextFieldNumber() {
       // The use of inline closures is to circumvent an issue where the compiler
diff --git a/Reference/CompileTests/MultiModule/Tests/Test2/uses_a_transitively2.pb.swift b/Reference/CompileTests/MultiModule/Tests/Test2/uses_a_transitively2.pb.swift
index 7dd0c210e..6c056cb8a 100644
--- a/Reference/CompileTests/MultiModule/Tests/Test2/uses_a_transitively2.pb.swift
+++ b/Reference/CompileTests/MultiModule/Tests/Test2/uses_a_transitively2.pb.swift
@@ -10,9 +10,7 @@
 import Foundation
 import SwiftProtobuf
 
-import ImportsAPublicly
 import ImportsImportsAPublicly
-import ModuleA
 
 // If the compiler emits an error on this type, it is because this file
 // was generated by a version of the `protoc` Swift plug-in that is
@@ -64,6 +62,11 @@ extension UsesATransitively2: SwiftProtobuf.Message, SwiftProtobuf._MessageImple
     122: .same(proto: "e"),
   ]
 
+  public var isInitialized: Bool {
+    if let v = self._a, !v.isInitialized {return false}
+    return true
+  }
+
   public mutating func decodeMessage<D: SwiftProtobuf.Decoder>(decoder: inout D) throws {
     while let fieldNumber = try decoder.nextFieldNumber() {
       // The use of inline closures is to circumvent an issue where the compiler
diff --git a/Sources/SwiftProtobufPluginLibrary/ProtoFileToModuleMappings.swift b/Sources/SwiftProtobufPluginLibrary/ProtoFileToModuleMappings.swift
index df21faf33..5b8549521 100644
--- a/Sources/SwiftProtobufPluginLibrary/ProtoFileToModuleMappings.swift
+++ b/Sources/SwiftProtobufPluginLibrary/ProtoFileToModuleMappings.swift
@@ -132,6 +132,14 @@ public struct ProtoFileToModuleMappings {
       }
     }
 
+    // NOTE: This api is only used by gRPC (or things like it), with
+    // `import public` now re-exporting things, this likely can go away or just
+    // be reduced just the above loop, without the need for special casing the
+    // `import public` cases. It will come down to what should expectations
+    // be for protobuf messages, enums, and extensions with repsect to something
+    // that generates on top if it. i.e. - should they re-export things or
+    // should only the generated proto code do it?
+
     // Protocol Buffers has the concept of "public imports", these are imports
     // into a file that expose everything from within the file to the new
     // context. From the docs -
diff --git a/Sources/SwiftProtobufPluginLibrary/SwiftProtobufNamer.swift b/Sources/SwiftProtobufPluginLibrary/SwiftProtobufNamer.swift
index 83942d7b2..0dab8324c 100644
--- a/Sources/SwiftProtobufPluginLibrary/SwiftProtobufNamer.swift
+++ b/Sources/SwiftProtobufPluginLibrary/SwiftProtobufNamer.swift
@@ -17,8 +17,8 @@ import Foundation
 public final class SwiftProtobufNamer {
   var filePrefixCache = [String:String]()
   var enumValueRelativeNameCache = [String:String]()
-  var mappings: ProtoFileToModuleMappings
-  var targetModule: String
+  public let mappings: ProtoFileToModuleMappings
+  public let targetModule: String
 
   public var swiftProtobufModuleName: String { return mappings.swiftProtobufModuleName }
 
diff --git a/Sources/SwiftProtobufTestHelpers/Descriptor+TestHelpers.swift b/Sources/SwiftProtobufTestHelpers/Descriptor+TestHelpers.swift
index 263e988db..817b853d4 100644
--- a/Sources/SwiftProtobufTestHelpers/Descriptor+TestHelpers.swift
+++ b/Sources/SwiftProtobufTestHelpers/Descriptor+TestHelpers.swift
@@ -11,12 +11,13 @@
 import SwiftProtobuf
 
 public extension Google_Protobuf_FileDescriptorProto {
-  init(name: String, dependencies: [String] = [], publicDependencies: [Int32] = []) {
+  init(name: String, dependencies: [String] = [], publicDependencies: [Int32] = [], package: String = "") {
     for idx in publicDependencies { precondition(Int(idx) <= dependencies.count) }
     self.init()
     self.name = name
-    dependency = dependencies
-    publicDependency = publicDependencies
+    self.dependency = dependencies
+    self.publicDependency = publicDependencies
+    self.package = package
   }
   init(textFormatStrings: [String]) throws {
     let s = textFormatStrings.joined(separator: "\n") + "\n"
@@ -27,7 +28,7 @@ public extension Google_Protobuf_FileDescriptorProto {
 public extension Google_Protobuf_FileDescriptorSet {
   init(files: [Google_Protobuf_FileDescriptorProto]) {
     self.init()
-    file = files
+    self.file = files
   }
   init(file: Google_Protobuf_FileDescriptorProto) {
     self.init()
diff --git a/Sources/protoc-gen-swift/Descriptor+Extensions.swift b/Sources/protoc-gen-swift/Descriptor+Extensions.swift
index 0cb60effe..0aaa00e67 100644
--- a/Sources/protoc-gen-swift/Descriptor+Extensions.swift
+++ b/Sources/protoc-gen-swift/Descriptor+Extensions.swift
@@ -14,6 +14,150 @@ extension FileDescriptor {
   var isBundledProto: Bool {
     return SwiftProtobufInfo.isBundledProto(file: self)
   }
+
+  // Returns a string of any import lines for the give file based on the file's
+  // imports. The string may include multiple lines.
+  //
+  // Protocol Buffers has the concept of "public imports", these are imports
+  // into a file that expose everything from within the file to the new
+  // context. From the docs -
+  // https://protobuf.dev/programming-guides/proto/#importing
+  //   `import public` dependencies can be transitively relied upon by anyone
+  //    importing the proto containing the import public statement.
+  // To properly expose the types for use, it means in each file, the public
+  // imports from the dependencies (recursively) have to be hoisted and
+  // reexported. This way someone importing a given module still sees the type
+  // even when moved.
+  //
+  // NOTE: There is a weakness for Swift with protobuf extensions. To make
+  // the protobuf extensions easier to use, a Swift extension is declared with
+  // field exposed as a property on the exteneded message. There is no way
+  // to reexport the Swift `extension` and/or added properties. But the raw
+  // types are re-exported to minimize the breaking of code if a type is moved
+  // between files/modules.
+  //
+  // `reexportPublicImports` will cause the `import public` types to be
+  // reexported to avoid breaking downstream code using a type that might have
+  // moved between .proto files.
+  //
+  // `asImplementationOnly` will cause all of the import directives to be
+  // marked as `@_implementationOnly`. It will also cause all of the `file`'s
+  // `publicDependencies` to instead be recursively pulled up as direct imports
+  // to ensure the generate file compiles, and no `import public` files are
+  // re-exported.
+  //
+  // Aside: This could be moved into the plugin library, but it doesn't seem
+  // like anyone else would need the logic. Swift GRPC support probably stick
+  // with the support for the module mappings.
+  public func computeImports(
+    namer: SwiftProtobufNamer,
+    reexportPublicImports: Bool,
+    asImplementationOnly: Bool
+  ) -> String {
+    // The namer should be configured with the module this file generated for.
+    assert(namer.targetModule == (namer.mappings.moduleName(forFile: self) ?? ""))
+    // Both options can't be enabled.
+    assert(!reexportPublicImports ||
+           !asImplementationOnly ||
+           reexportPublicImports != asImplementationOnly)
+
+    guard namer.mappings.hasMappings else {
+      // No module mappings? Everything must be the same module, so no Swift
+      // imports will be needed.
+      return ""
+    }
+
+    if dependencies.isEmpty {
+      // No proto dependencies (imports), then no Swift imports will be needed.
+      return ""
+    }
+
+    let directive = asImplementationOnly ? "@_implementationOnly import" : "import"
+    var imports = Set<String>()
+    for dependency in dependencies {
+      if SwiftProtobufInfo.isBundledProto(file: dependency) {
+        continue  // No import needed for the runtime, that's always added.
+      }
+      if reexportPublicImports && publicDependencies.contains(where: { $0 === dependency }) {
+        // When re-exporting, the `import public` types will be imported
+        // instead of importing the module.
+        continue
+      }
+      if let depModule = namer.mappings.moduleName(forFile: dependency),
+         depModule != namer.targetModule {
+        // Different module, import it.
+        imports.insert("\(directive) \(depModule)")
+      }
+    }
+
+    // If not re-exporting imports, then there is nothing special needed for
+    // `import public` files, as any transitive `import public` directives
+    // would have already re-exported the types, so everything this file needs
+    // will be covered by the above imports.
+    let exportingImports: [String] =
+      reexportPublicImports ? computeSymbolReExports(namer: namer) : [String]()
+
+    var result = imports.sorted().joined(separator: "\n")
+    if !exportingImports.isEmpty {
+      if !result.isEmpty {
+        result.append("\n")
+      }
+      result.append("// Use of 'import public' causes re-exports:\n")
+      result.append(exportingImports.sorted().joined(separator: "\n"))
+    }
+    return result
+  }
+
+  // Internal helper to `computeImports(...)`.
+  private func computeSymbolReExports(namer: SwiftProtobufNamer) -> [String] {
+    var result = [String]()
+
+    // To handle re-exporting, recuively walk all the `import public` files
+    // and make this module do a Swift exporting import of the specific
+    // symbols. That will keep any type that gets moved between .proto files
+    // still exposed from the same modules so as not to break developer
+    // authored code.
+    var toScan = publicDependencies
+    var visited = Set<String>()
+    while let dependency = toScan.popLast() {
+      let dependencyName = dependency.name
+      if visited.contains(dependencyName) { continue }
+      visited.insert(dependencyName)
+
+      if SwiftProtobufInfo.isBundledProto(file: dependency) {
+        continue  // Bundlined file, nothing to do.
+      }
+      guard let depModule = namer.mappings.moduleName(forFile: dependency) else {
+        continue  // No mapping, assume same module, nothing to do.
+      }
+      if depModule == namer.targetModule {
+        // Same module, nothing to do (that generated file will do any re-exports).
+        continue
+      }
+
+      toScan.append(contentsOf: dependency.publicDependencies)
+
+      // NOTE: This re-exports/imports from the module that defines the type.
+      // If Xcode/SwiftPM ever were to do some sort of "layering checks" to
+      // ensure there is a direct dependency on the thing being imported, this
+      // could be updated do the re-export/import from the middle step in
+      // chained imports.
+
+      for m in dependency.messages {
+        result.append("@_exported import struct \(namer.fullName(message: m))")
+      }
+      for e in dependency.enums {
+        result.append("@_exported import enum \(namer.fullName(enum: e))")
+      }
+      // There is nothing we can do for the Swift extensions declared on the
+      // extended Messages, best we can do is expose the raw extenions
+      // themselves.
+      for e in dependency.extensions {
+        result.append("@_exported import let \(namer.fullName(extensionField: e))")
+      }
+    }
+    return result
+  }
 }
 
 extension Descriptor {
diff --git a/Sources/protoc-gen-swift/FileGenerator.swift b/Sources/protoc-gen-swift/FileGenerator.swift
index e4055805a..18e46bbe3 100644
--- a/Sources/protoc-gen-swift/FileGenerator.swift
+++ b/Sources/protoc-gen-swift/FileGenerator.swift
@@ -90,25 +90,20 @@ class FileGenerator {
 
         p.print("\(comments)import Foundation")
 
-        // Import all other imports as @_implementationOnly if the option is
-        // set, to avoid exposing internal types to users.
-        let visibilityAnnotation: String
-        if self.generatorOptions.implementationOnlyImports {
-            precondition(self.generatorOptions.visibility == .internal)
-            visibilityAnnotation = "@_implementationOnly "
-        } else {
-            visibilityAnnotation = ""
-        }
         if fileDescriptor.isBundledProto {
             p.print("// 'import \(namer.swiftProtobufModuleName)' suppressed, this proto file is meant to be bundled in the runtime.")
         } else {
-            p.print("\(visibilityAnnotation)import \(namer.swiftProtobufModuleName)")
+            let directive = self.generatorOptions.implementationOnlyImports ? "@_implementationOnly import" : "import"
+            p.print("\(directive) \(namer.swiftProtobufModuleName)")
         }
-        if let neededImports = generatorOptions.protoToModuleMappings.neededModules(forFile: fileDescriptor) {
+
+        let neededImports = fileDescriptor.computeImports(
+          namer: namer,
+          reexportPublicImports: self.generatorOptions.visibility != .internal,
+          asImplementationOnly: self.generatorOptions.implementationOnlyImports)
+        if !neededImports.isEmpty {
             p.print()
-            for i in neededImports {
-                p.print("\(visibilityAnnotation)import \(i)")
-            }
+            p.print(neededImports)
         }
 
         p.print()
diff --git a/Tests/protoc-gen-swiftTests/Test_DescriptorExtensions.swift b/Tests/protoc-gen-swiftTests/Test_DescriptorExtensions.swift
index 712070cb1..1c2a342eb 100644
--- a/Tests/protoc-gen-swiftTests/Test_DescriptorExtensions.swift
+++ b/Tests/protoc-gen-swiftTests/Test_DescriptorExtensions.swift
@@ -13,6 +13,8 @@ import SwiftProtobuf
 import SwiftProtobufPluginLibrary
 @testable import protoc_gen_swift
 
+fileprivate typealias FileDescriptorProto = Google_Protobuf_FileDescriptorProto
+
 final class Test_DescriptorExtensions: XCTestCase {
 
   func testExtensionRanges() throws {
@@ -194,4 +196,271 @@ final class Test_DescriptorExtensions: XCTestCase {
     XCTAssertIdentical(aliasInfo.original(of: e.values[5]), e.values[0])
   }
 
+  func test_File_computeImports_noImportPublic() {
+    let configText = """
+      mapping { module_name: "foo", proto_file_path: "file" }
+      mapping { module_name: "bar", proto_file_path: "dir1/file" }
+      mapping { module_name: "baz", proto_file_path: ["dir2/file","file4"] }
+      mapping { module_name: "foo", proto_file_path: "file5" }
+    """
+
+    let config = try! SwiftProtobuf_GenSwift_ModuleMappings(textFormatString: configText)
+    let mapper = try! ProtoFileToModuleMappings(moduleMappingsProto: config)
+
+    let fileProtos = [
+      FileDescriptorProto(name: "file"),
+      FileDescriptorProto(name: "google/protobuf/any.proto", package: "google.protobuf"),
+      FileDescriptorProto(name: "dir1/file", dependencies: ["file"]),
+      FileDescriptorProto(name: "dir2/file", dependencies: ["google/protobuf/any.proto"]),
+      FileDescriptorProto(name: "file4", dependencies: ["dir2/file", "dir1/file", "file"]),
+      FileDescriptorProto(name: "file5", dependencies: ["file"]),
+    ]
+    let descSet = DescriptorSet(protos: fileProtos)
+
+    // ( filename, imports, implOnly imports )
+    let tests: [(String, String, String)] = [
+      ( "file", "", "" ),
+      ( "dir1/file", "import foo", "@_implementationOnly import foo" ),
+      ( "dir2/file", "", "" ),
+      ( "file4", "import bar\nimport foo", "@_implementationOnly import bar\n@_implementationOnly import foo" ),
+      ( "file5", "", "" ),
+    ]
+
+    for (name, expected, expectedImplOnly) in tests {
+      let fileDesc = descSet.files.filter{ $0.name == name }.first!
+      do {  // reexportPublicImports: false, asImplementationOnly: false
+        let namer =
+          SwiftProtobufNamer(currentFile: fileDesc,
+                             protoFileToModuleMappings: mapper)
+        let result = fileDesc.computeImports(namer: namer, reexportPublicImports: false, asImplementationOnly: false)
+        XCTAssertEqual(result, expected, "Looking for \(name)")
+      }
+      do {  // reexportPublicImports: true, asImplementationOnly: false - No `import publc`, same as previous
+        let namer =
+          SwiftProtobufNamer(currentFile: fileDesc,
+                             protoFileToModuleMappings: mapper)
+        let result = fileDesc.computeImports(namer: namer, reexportPublicImports: true, asImplementationOnly: false)
+        XCTAssertEqual(result, expected, "Looking for \(name)")
+      }
+      do {  // reexportPublicImports: false, asImplementationOnly: true
+        let namer =
+          SwiftProtobufNamer(currentFile: fileDesc,
+                             protoFileToModuleMappings: mapper)
+        let result = fileDesc.computeImports(namer: namer, reexportPublicImports: false, asImplementationOnly: true)
+        XCTAssertEqual(result, expectedImplOnly, "Looking for \(name)")
+      }
+    }
+  }
+
+  func test_File_computeImports_PublicImports() {
+    // See the notes on computeImports(namer:reexportPublicImports:asImplementationOnly:)
+    // about how public import complicate things.
+
+    // Given:
+    //
+    //  + File: a.proto
+    //    message A {}
+    //
+    //    enum E {
+    //      E_UNSET = 0;
+    //      E_A = 1;
+    //      E_B = 2;
+    //    }
+    //
+    //  + File: imports_a_publicly.proto
+    //    import public "a.proto";
+    //
+    //    message ImportsAPublicly {
+    //      optional A a = 1;
+    //      optional E e = 2;
+    //    }
+    //
+    //  + File: imports_imports_a_publicly.proto
+    //    import public "imports_a_publicly.proto";
+    //
+    //    message ImportsImportsAPublicly {
+    //      optional A a = 1;
+    //    }
+    //
+    //  + File: uses_a_transitively.proto
+    //    import "imports_a_publicly.proto";
+    //
+    //    message UsesATransitively {
+    //      optional A a = 1;
+    //    }
+    //
+    //  + File: uses_a_transitively2.proto
+    //    import "imports_imports_a_publicly.proto";
+    //
+    //    message UsesATransitively2 {
+    //      optional A a = 1;
+    //    }
+    //
+    // With a mapping file of:
+    //
+    //    mapping {
+    //      module_name: "A"
+    //      proto_file_path: "a.proto"
+    //    }
+    //    mapping {
+    //      module_name: "ImportsAPublicly"
+    //      proto_file_path: "imports_a_publicly.proto"
+    //    }
+    //    mapping {
+    //      module_name: "ImportsImportsAPublicly"
+    //      proto_file_path: "imports_imports_a_publicly.proto"
+    //    }
+
+    let configText = """
+      mapping { module_name: "A", proto_file_path: "a.proto" }
+      mapping { module_name: "ImportsAPublicly", proto_file_path: "imports_a_publicly.proto" }
+      mapping { module_name: "ImportsImportsAPublicly", proto_file_path: "imports_imports_a_publicly.proto" }
+    """
+
+    let config = try! SwiftProtobuf_GenSwift_ModuleMappings(textFormatString: configText)
+    let mapper = try! ProtoFileToModuleMappings(moduleMappingsProto: config)
+
+    let fileProtos = [
+      try! FileDescriptorProto(textFormatString: """
+        name: "a.proto"
+        message_type {
+          name: "A"
+        }
+        enum_type {
+          name: "E"
+          value {
+            name: "E_UNSET"
+            number: 0
+          }
+          value {
+            name: "E_A"
+            number: 1
+          }
+          value {
+            name: "E_B"
+            number: 2
+          }
+        }
+      """),
+      try! FileDescriptorProto(textFormatString: """
+        name: "imports_a_publicly.proto"
+        dependency: "a.proto"
+        message_type {
+          name: "ImportsAPublicly"
+          field {
+            name: "a"
+            number: 1
+            label: LABEL_OPTIONAL
+            type: TYPE_MESSAGE
+            type_name: ".A"
+            json_name: "a"
+          }
+          field {
+            name: "e"
+            number: 2
+            label: LABEL_OPTIONAL
+            type: TYPE_ENUM
+            type_name: ".E"
+            json_name: "e"
+          }
+        }
+        public_dependency: 0
+      """),
+      try! FileDescriptorProto(textFormatString: """
+        name: "imports_imports_a_publicly.proto"
+        dependency: "imports_a_publicly.proto"
+        message_type {
+          name: "ImportsImportsAPublicly"
+          field {
+            name: "a"
+            number: 1
+            label: LABEL_OPTIONAL
+            type: TYPE_MESSAGE
+            type_name: ".A"
+            json_name: "a"
+          }
+        }
+        public_dependency: 0
+      """),
+      try! FileDescriptorProto(textFormatString: """
+        name: "uses_a_transitively.proto"
+        dependency: "imports_a_publicly.proto"
+        message_type {
+          name: "UsesATransitively"
+          field {
+            name: "a"
+            number: 1
+            label: LABEL_OPTIONAL
+            type: TYPE_MESSAGE
+            type_name: ".A"
+            json_name: "a"
+          }
+        }
+      """),
+      try! FileDescriptorProto(textFormatString: """
+        name: "uses_a_transitively2.proto"
+        dependency: "imports_imports_a_publicly.proto"
+        message_type {
+          name: "UsesATransitively2"
+          field {
+            name: "a"
+            number: 1
+            label: LABEL_OPTIONAL
+            type: TYPE_MESSAGE
+            type_name: ".A"
+            json_name: "a"
+          }
+        }
+      """),
+    ]
+    let descSet = DescriptorSet(protos: fileProtos)
+
+    // ( filename, imports, reExportPublicImports imports, implOnly imports )
+    let tests: [(String, String, String, String)] = [
+      ( "a.proto",
+        "", "", "" ),
+      ( "imports_a_publicly.proto",
+        "import A",
+        "// Use of 'import public' causes re-exports:\n@_exported import enum A.E\n@_exported import struct A.A",
+        "@_implementationOnly import A" ),
+      ( "imports_imports_a_publicly.proto",
+        "import ImportsAPublicly",
+        "// Use of 'import public' causes re-exports:\n@_exported import enum A.E\n@_exported import struct A.A\n@_exported import struct ImportsAPublicly.ImportsAPublicly",
+        "@_implementationOnly import ImportsAPublicly" ),
+      ( "uses_a_transitively.proto",
+        "import ImportsAPublicly",  // this reexports A, so we don't directly pull in A.
+        "import ImportsAPublicly",  // just a plain `import`, nothing to re-export.
+        "@_implementationOnly import ImportsAPublicly" ),
+      ( "uses_a_transitively2.proto",
+        "import ImportsImportsAPublicly",  // this chain reexports A, so we don't directly pull in A.
+        "import ImportsImportsAPublicly",  // just a plain `import`, nothing to re-export.
+        "@_implementationOnly import ImportsImportsAPublicly" ),
+    ]
+
+    for (name, expected, expectedReExport, expectedImplOnly) in tests {
+      let fileDesc = descSet.files.filter{ $0.name == name }.first!
+      do {  // reexportPublicImports: false, asImplementationOnly: false
+        let namer =
+          SwiftProtobufNamer(currentFile: fileDesc,
+                             protoFileToModuleMappings: mapper)
+        let result = fileDesc.computeImports(namer: namer, reexportPublicImports: false, asImplementationOnly: false)
+        XCTAssertEqual(result, expected, "Looking for \(name)")
+      }
+      do {  // reexportPublicImports: true, asImplementationOnly: false
+        let namer =
+          SwiftProtobufNamer(currentFile: fileDesc,
+                             protoFileToModuleMappings: mapper)
+        let result = fileDesc.computeImports(namer: namer, reexportPublicImports: true, asImplementationOnly: false)
+        XCTAssertEqual(result, expectedReExport, "Looking for \(name)")
+      }
+      do {  // reexportPublicImports: false, asImplementationOnly: true
+        let namer =
+          SwiftProtobufNamer(currentFile: fileDesc,
+                             protoFileToModuleMappings: mapper)
+        let result = fileDesc.computeImports(namer: namer, reexportPublicImports: false, asImplementationOnly: true)
+        XCTAssertEqual(result, expectedImplOnly, "Looking for \(name)")
+      }
+    }
+  }
+
 }