From e4ec79b5f3f8ab73de83d43fd9e431a7740c457e Mon Sep 17 00:00:00 2001
From: Matt Metlis <matt.metlis@twosigma.com>
Date: Wed, 4 Sep 2019 14:05:20 -0400
Subject: [PATCH] #37 Updating isCachedClientSide method to ignore
 If-Modified-Since when If-None-Match is also specified.

---
 .../bundles/assets/AssetServlet.java          | 23 ++++++--
 .../bundles/assets/AssetServletTest.java      | 52 +++++++++++++++++++
 2 files changed, 72 insertions(+), 3 deletions(-)

diff --git a/src/main/java/io/dropwizard/bundles/assets/AssetServlet.java b/src/main/java/io/dropwizard/bundles/assets/AssetServlet.java
index 8c79999..84c4e19 100644
--- a/src/main/java/io/dropwizard/bundles/assets/AssetServlet.java
+++ b/src/main/java/io/dropwizard/bundles/assets/AssetServlet.java
@@ -231,9 +231,26 @@ protected void doGet(HttpServletRequest req, HttpServletResponse resp)
   }
 
   private boolean isCachedClientSide(HttpServletRequest req, Asset cachedAsset) {
-    return cachedAsset.getETag().equals(req.getHeader(HttpHeaders.IF_NONE_MATCH))
-            || (req.getDateHeader(HttpHeaders.IF_MODIFIED_SINCE)
-            >= cachedAsset.getLastModifiedTime());
+    String ifNoneMatchHeader = req.getHeader(HttpHeaders.IF_NONE_MATCH);
+    long ifModifiedSinceHeader = req.getDateHeader(HttpHeaders.IF_MODIFIED_SINCE);
+
+    boolean ifNoneMatchHeaderExists = ifNoneMatchHeader != null && !ifNoneMatchHeader.isEmpty();
+    boolean ifModifiedSinceHeaderExists = ifModifiedSinceHeader >= 0;
+
+    // If there is an If-None-Match header, determine caching based on eTag.
+    // Per RFC 7232, if If-None-Match is present, ignore If-Modified-Since.
+    if (ifNoneMatchHeaderExists) {
+      return cachedAsset.getETag().equals(ifNoneMatchHeader);
+    } else if (ifModifiedSinceHeaderExists) {
+      // If there is no If-None-Match header, but there is an If-Modified-Since header,
+      // determine caching based on last modified time.
+      return ifModifiedSinceHeader >= cachedAsset.getLastModifiedTime();
+    } else {
+      // If there is neither an If-None-Match header nor am If-Modified-Since header,
+      // we cannot determine that the entity is cached.
+      return false;
+    }
+
   }
 
   /**
diff --git a/src/test/java/io/dropwizard/bundles/assets/AssetServletTest.java b/src/test/java/io/dropwizard/bundles/assets/AssetServletTest.java
index 7970f70..38668fb 100644
--- a/src/test/java/io/dropwizard/bundles/assets/AssetServletTest.java
+++ b/src/test/java/io/dropwizard/bundles/assets/AssetServletTest.java
@@ -410,6 +410,58 @@ public void supportsIfModifiedSinceRequests() throws Exception {
             .isEqualTo(304);
   }
 
+  @Test
+  // Verify conformance with the HTTP/1.1 spec which requires ignoring the If-Modified-Since
+  // header when the If-None-Match header is present (RFC 7232).
+  public void supportsIfNoneMatchAndIfModifiedSinceRequests() throws Exception {
+    response = makeRequest();
+    final long lastModifiedTime = response.getDateField(HttpHeaders.LAST_MODIFIED);
+    final String correctEtag = response.get(HttpHeaders.ETAG);
+
+    request.putDateField(HttpHeaders.IF_MODIFIED_SINCE, lastModifiedTime);
+    request.setHeader(HttpHeaders.IF_NONE_MATCH, correctEtag);
+    response = makeRequest();
+    final int statusWithMatchingLastModifiedTimeAndMatchingEtag = response.getStatus();
+
+    request.putDateField(HttpHeaders.IF_MODIFIED_SINCE, lastModifiedTime - 100);
+    request.setHeader(HttpHeaders.IF_NONE_MATCH, correctEtag);
+    response = makeRequest();
+    final int statusWithStaleLastModifiedTimeAndMatchingEtag = response.getStatus();
+
+    request.putDateField(HttpHeaders.IF_MODIFIED_SINCE, lastModifiedTime + 100);
+    request.setHeader(HttpHeaders.IF_NONE_MATCH, correctEtag);
+    response = makeRequest();
+    final int statusWithRecentLastModifiedTimeAndMatchingEtag = response.getStatus();
+
+    request.putDateField(HttpHeaders.IF_MODIFIED_SINCE, lastModifiedTime);
+    request.setHeader(HttpHeaders.IF_NONE_MATCH, correctEtag + "FOO");
+    response = makeRequest();
+    final int statusWithMatchingLastModifiedTimeAndNonMatchingEtag = response.getStatus();
+
+    request.putDateField(HttpHeaders.IF_MODIFIED_SINCE, lastModifiedTime - 100);
+    request.setHeader(HttpHeaders.IF_NONE_MATCH, correctEtag + "FOO");
+    response = makeRequest();
+    final int statusWithStaleLastModifiedTimeAndNonMatchingEtag = response.getStatus();
+
+    request.putDateField(HttpHeaders.IF_MODIFIED_SINCE, lastModifiedTime + 100);
+    request.setHeader(HttpHeaders.IF_NONE_MATCH, correctEtag + "FOO");
+    response = makeRequest();
+    final int statusWithRecentLastModifiedTimeAndNonMatchingEtag = response.getStatus();
+
+    assertThat(statusWithMatchingLastModifiedTimeAndMatchingEtag)
+            .isEqualTo(304);
+    assertThat(statusWithStaleLastModifiedTimeAndMatchingEtag)
+            .isEqualTo(304);
+    assertThat(statusWithRecentLastModifiedTimeAndMatchingEtag)
+            .isEqualTo(304);
+    assertThat(statusWithMatchingLastModifiedTimeAndNonMatchingEtag)
+            .isEqualTo(200);
+    assertThat(statusWithStaleLastModifiedTimeAndNonMatchingEtag)
+            .isEqualTo(200);
+    assertThat(statusWithRecentLastModifiedTimeAndNonMatchingEtag)
+            .isEqualTo(200);
+  }
+
   @Test
   public void guessesMimeTypes() throws Exception {
     response = makeRequest();