Allow lazy header factories to return null values.

sjudd · sjudd · commit 66d4caa4d373 · 2015-11-06T11:45:01.000-08:00
After this change, we can try to lazily retrieve values for headers even when retrieving those values may fail (due to network operations or I/O). Previously the factories would have had to return some value. ------------- Created by MOE: https://github.com/google/moe MOE_MIGRATED_REVID=107154151
diff --git a/library/src/main/java/com/bumptech/glide/load/model/LazyHeaderFactory.java b/library/src/main/java/com/bumptech/glide/load/model/LazyHeaderFactory.java
@@ -1,5 +1,7 @@
 package com.bumptech.glide.load.model;
 
+import android.support.annotation.Nullable;
+
 /**
  * An interface for lazily creating headers that allows expensive to calculate headers (oauth for
  * example) to be generated in the background during the first fetch.
@@ -8,6 +10,15 @@
  */
 public interface LazyHeaderFactory {
 
+    /**
+     * Returns an http header, or {@code null} if no header could be built.
+     *
+     * <p>Returning {@code null} or an empty String from this method will result in this particular
+     * key/value being excluded from the headers provided in the request. If there are multiple
+     * factories or values for a particular key, any non-null values will still be included for that
+     * key.
+     */
+    @Nullable
     String buildHeader();
 
 }
diff --git a/library/src/main/java/com/bumptech/glide/load/model/LazyHeaders.java b/library/src/main/java/com/bumptech/glide/load/model/LazyHeaders.java
@@ -47,12 +47,18 @@ private Map<String, String> generateHeaders() {
       int size = factories.size();
       for (int i = 0; i < size; i++) {
         LazyHeaderFactory factory = factories.get(i);
-        sb.append(factory.buildHeader());
-        if (i != factories.size() - 1) {
-          sb.append(',');
+        String header = factory.buildHeader();
+        if (!TextUtils.isEmpty(header)) {
+          sb.append(header);
+          if (i != factories.size() - 1) {
+            sb.append(',');
+          }
         }
       }
-      combinedHeaders.put(entry.getKey(), sb.toString());
+      String values = sb.toString();
+      if (!TextUtils.isEmpty(values)) {
+        combinedHeaders.put(entry.getKey(), sb.toString());
+      }
     }
 
     return combinedHeaders;
diff --git a/library/src/test/java/com/bumptech/glide/load/model/LazyHeadersTest.java b/library/src/test/java/com/bumptech/glide/load/model/LazyHeadersTest.java
@@ -6,6 +6,8 @@
 
 import com.google.common.testing.EqualsTester;
 
+import android.support.annotation.Nullable;
+
 import com.bumptech.glide.load.model.LazyHeaders.Builder;
 
 import org.junit.After;
@@ -229,6 +231,55 @@ public void testRemovingAndAddingUserAgentHeaderReplacesDefaultThenAppends() {
     assertThat(headers.getHeaders()).containsEntry("User-Agent", "false,true");
   }
 
+  @Test
+  public void testKeyNotIncludedWithFactoryThatReturnsNullValue() {
+    Builder builder = new Builder();
+    builder.setHeader("test", new LazyHeaderFactory() {
+      @Nullable
+      @Override
+      public String buildHeader() {
+        return null;
+      }
+    });
+    LazyHeaders headers = builder.build();
+    assertThat(headers.getHeaders()).doesNotContainKey("test");
+  }
+
+  @Test
+  public void testKeyNotIncludedWithFactoryThatReturnsEmptyValue() {
+    Builder builder = new Builder();
+    builder.setHeader("test", new LazyHeaderFactory() {
+      @Nullable
+      @Override
+      public String buildHeader() {
+        return "";
+      }
+    });
+    LazyHeaders headers = builder.build();
+    assertThat(headers.getHeaders()).doesNotContainKey("test");
+  }
+
+  @Test
+  public void testKeyIncludedWithOneFactoryThatReturnsNullAndOneFactoryThatDoesNotReturnNull() {
+    Builder builder = new Builder();
+    builder.addHeader("test", new LazyHeaderFactory() {
+      @Nullable
+      @Override
+      public String buildHeader() {
+        return null;
+      }
+    });
+    builder.addHeader("test", new LazyHeaderFactory() {
+      @Nullable
+      @Override
+      public String buildHeader() {
+        return "value";
+      }
+    });
+    LazyHeaders headers = builder.build();
+    assertThat(headers.getHeaders()).containsEntry("test", "value");
+  }
+
   @Test
   public void testEquals() {
     LazyHeaderFactory firstLazyFactory = mock(LazyHeaderFactory.class);
