Merge pull request #137 from gabriel-samfira/omit-null-values

Add graph visitor that ignores null values
cloudbase · Aug 26, 2024 · 0d5b89f · 0d5b89f
2 parents 961aa95 + d7a60ee
commit 0d5b89f
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Showing 5 changed files with 88 additions and 8 deletions.
diff --git a/Tests/powershell-yaml.Tests.ps1 b/Tests/powershell-yaml.Tests.ps1
@@ -54,6 +54,11 @@ iAmEmptyString: ""
 "@
             }
 
+            It "should not serialize null value when -Options OmitNullValues is set" {
+                $toYaml = ConvertTo-Yaml $nullAndString -Options OmitNullValues
+                $toYaml | Should -Be "iAmEmptyString: """"$([Environment]::NewLine)"
+            }
+
             It "should preserve nulls and empty strings from PowerShell" {
                 $toYaml = ConvertTo-Yaml $nullAndString
                 $backFromYaml = ConvertFrom-Yaml $toYaml
@@ -552,6 +557,7 @@ int64: 9223372036854775807
                 $PsO = [PSCustomObject]@{
                     Name = 'Value'
                     Nested = $nestedPsO
+                    NullValue = $null
                 }
 
                 class TestClass {
@@ -569,11 +575,38 @@ int64: 9223372036854775807
                 $ret["PsO"]["Name"] = "Value"
                 $ret["PsO"]["Nested"] = [System.Collections.Specialized.OrderedDictionary]::new()
                 $ret["PsO"]["Nested"]["Nested"] = "NestedValue"
+                $ret["PsO"]["NullValue"] = $null
                 $ret["Ok"] = "aye"
                 Assert-Equivalent -Options $compareStrictly -Expected $ret -Actual $result
             }
         }
 
+        Context 'PSObject with null value is skipped when -Options OmitNullValues' {
+            BeforeAll {
+                $global:value = [PSCustomObject]@{
+                    key1 = "value1"
+                    key2 = $null
+                }
+            }
+            It 'Should serialise as a hash with only the non-null value' {
+                $result = ConvertTo-Yaml $value -Options OmitNullValues
+                $result | Should -Be "key1: value1$([Environment]::NewLine)"
+            }
+        }
+
+        Context 'PSObject with null value is included when -Options OmitNullValues is not set' {
+            BeforeAll {
+                $global:value = [PSCustomObject]@{
+                    key1 = "value1"
+                    key2 = $null
+                }
+            }
+            It 'Should serialise as a hash with the null value' {
+                $result = ConvertTo-Yaml $value
+                $result | Should -Be "key1: value1$([Environment]::NewLine)key2: $null$([Environment]::NewLine)"
+            }
+        }
+
         Context 'PSCustomObject with a single property' {
             BeforeAll {
                 $global:value = [PSCustomObject]@{key="value"}

diff --git a/lib/net47/StringQuotingEmitter.dll b/lib/net47/StringQuotingEmitter.dll
diff --git a/lib/netstandard2.1/StringQuotingEmitter.dll b/lib/netstandard2.1/StringQuotingEmitter.dll
diff --git a/powershell-yaml.psm1 b/powershell-yaml.psm1
@@ -22,6 +22,7 @@ enum SerializationOptions {
     JsonCompatible = 8
     DefaultToStaticType = 16
     WithIndentedSequences = 32
+    OmitNullValues = 64
 }
 $here = Split-Path -Parent $MyInvocation.MyCommand.Path
 $infinityRegex = [regex]::new('^[-+]?(\.inf|\.Inf|\.INF)$', "Compiled, CultureInvariant");
@@ -408,8 +409,12 @@ function Get-Serializer {
     if ($Options.HasFlag([SerializationOptions]::WithIndentedSequences)) {
         $builder = $builder.WithIndentedSequences()
     }
+
+    $omitNull = $Options.HasFlag([SerializationOptions]::OmitNullValues)
+
     $stringQuoted = $stringQuotedAssembly.GetType("StringQuotingEmitter")
-    $builder = $stringQuoted::Add($builder)
+    $builder = $stringQuoted::Add($builder, $omitNull)
+
     return $builder.Build()
 }
 

diff --git a/src/serializer.cs b/src/serializer.cs
@@ -8,7 +8,29 @@
 using YamlDotNet.Serialization;
 using YamlDotNet.Serialization.EventEmitters;
 using YamlDotNet.Core.Events;
+using YamlDotNet.Serialization.ObjectGraphVisitors;
 
+public sealed class NullValueGraphVisitor : ChainedObjectGraphVisitor
+{
+    public NullValueGraphVisitor(IObjectGraphVisitor<IEmitter> nextVisitor)
+        : base(nextVisitor)
+    {
+    }
+
+    public override bool EnterMapping(IPropertyDescriptor key, IObjectDescriptor value, IEmitter context, ObjectSerializer serializer) {
+        if (value.Value == null) {
+            return false;
+        }
+        return base.EnterMapping(key, value, context, serializer);
+    }
+
+    public override bool EnterMapping(IObjectDescriptor key, IObjectDescriptor value, IEmitter context, ObjectSerializer serializer) {
+        if (value.Value == null) {
+            return false;
+        }
+        return base.EnterMapping(key, value, context, serializer);
+    }
+}
 
 public class BigIntegerTypeConverter : IYamlTypeConverter {
     public bool Accepts(Type type) {
@@ -28,6 +50,13 @@ public void WriteYaml(IEmitter emitter, object value, Type type, ObjectSerialize
 }
 
 public class PSObjectTypeConverter : IYamlTypeConverter {
+
+    private bool omitNullValues;
+
+    public PSObjectTypeConverter(bool omitNullValues = false) {
+        this.omitNullValues = omitNullValues;
+    }
+
     public bool Accepts(Type type) {
         return typeof(PSObject).IsAssignableFrom(type);
     }
@@ -39,13 +68,21 @@ public object ReadYaml(IParser parser, Type type, ObjectDeserializer rootDeseria
         return deserializedObject;
     }
 
-    public void WriteYaml(IEmitter emitter, object value, Type type, ObjectSerializer serializer) {        
+    public void WriteYaml(IEmitter emitter, object value, Type type, ObjectSerializer serializer) {
         var psObj = (PSObject)value;
 
         emitter.Emit(new MappingStart());
         foreach (var prop in psObj.Properties) {
-            serializer(prop.Name, prop.Name.GetType());
-            serializer(prop.Value, prop.Value.GetType());
+            if (prop.Value == null) {
+                if (this.omitNullValues == true) {
+                    continue;
+                }
+                serializer(prop.Name, prop.Name.GetType());
+                emitter.Emit(new Scalar(AnchorName.Empty, "tag:yaml.org,2002:null", "", ScalarStyle.Plain, true, false));
+            } else {
+                serializer(prop.Name, prop.Name.GetType());
+                serializer(prop.Value, prop.Value.GetType());
+            }
         }
         emitter.Emit(new MappingEnd());
     }
@@ -81,10 +118,15 @@ public override void Emit(ScalarEventInfo eventInfo, IEmitter emitter) {
         base.Emit(eventInfo, emitter);
     }
     // objectGraphVisitor, w => w.OnTop()
-    public static SerializerBuilder Add(SerializerBuilder builder) {
-        return builder 
+    public static SerializerBuilder Add(SerializerBuilder builder, bool omitNullValues = false) {
+        builder = builder
             .WithEventEmitter(next => new StringQuotingEmitter(next))
             .WithTypeConverter(new BigIntegerTypeConverter())
-            .WithTypeConverter(new PSObjectTypeConverter());
+            .WithTypeConverter(new PSObjectTypeConverter(omitNullValues));
+        if (omitNullValues == true) {
+            builder = builder
+                .WithEmissionPhaseObjectGraphVisitor(args => new NullValueGraphVisitor(args.InnerVisitor));
+        }
+        return builder;
     }
-}
+}