Make CTS more opinionated about the platform's default MimeMap.

Historically, the mapping implemented by MimeMap (formerly MimeUtils)
was largely untested and therefore differed between Android devices.

This CL topic makes CtsMimeMapTestCases a lot more opinionated by
checking that:

 - MimeMap.getDefault() must respect all of the mappings supplied
   in stock Android. This is enforced via CTS bundling a copy of:
   - the {,android.,vendor.}mime.types data files
   - DefaultMimeMapFactory (rewritten via jarjar to
     android.content.type.cts.StockAndroidMimeMapFactory)
   MimeMap.getDefault() is allowed to implement _additional_
   mappings, but changed or removed mappings are not allowed.
 - Public APIs android.webkit.MimeTypeMap and
   URLConnection.getFileNameMap() must behave consistently with
   MimeMap.getDefault() (in stock Android, those APIs are
   implemented directly on top of MimeMap.getDefault()).

Test: atest CtsMimeMapTestCases
Test: atest CtsLibcoreTestCases:libcore.libcore.net.MimeMapTest
Test: The above atest runs pass on a device that contains an
      additional mapping in vendor.mime.types that is not
      present in CTS.
Test: Checked that on a device that changes a mapping in
      android.mime.types, CtsLibcoreTestCases still passes
      but CtsMimeMapTestCases fails.

Bug: 141842930
Bug: 139895945

Change-Id: I68e0e9c3ce53c1acf2a89f8b80519f4658c07217

3 files changed, 91 insertions, 15 deletions

diff --git a/mime/Android.bp b/mime/Android.bp
index 0ae94d44061d..51290f6b1176 100644
--- a/mime/Android.bp
+++ b/mime/Android.bp
@@ -12,24 +12,84 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+
+java_defaults {
+    name: "mimemap-defaults",
+    srcs: [
+        "java/android/content/type/DefaultMimeMapFactory.java",
+    ],
+    sdk_version: "core_platform",
+}
+
 java_library {
     name: "mimemap",
+    defaults: ["mimemap-defaults"],
+    static_libs: ["mimemap-res.jar"],
+    visibility: [
+        "//frameworks/base:__subpackages__",
+    ],
+}
+
+java_library {
+    name: "mimemap-testing",
+    defaults: ["mimemap-defaults"],
+    static_libs: ["mimemap-testing-res.jar"],
+    jarjar_rules: "jarjar-rules.txt",
     visibility: [
         "//cts/tests/tests/mimemap:__subpackages__",
         "//frameworks/base:__subpackages__",
     ],
+}
+
+// The mimemap-res.jar and mimemap-testing-res.jar genrules produce a .jar that
+// has the resource file in a subdirectory res/ and testres/, respectively.
+// Those paths need to They need to be in different paths because one of them
+// ends up on a bootclasspath jar whereas the other one ends up in a test jar.
+// Bootclasspath resources hide test or application resources under the same
+// path because ClassLoader.getResource(String) consults the parent ClassLoader
+// first.
+//
+// Further notes:
+//  - the "cp" command will flatten any directory paths that occur in $(in),
+//    but here they happen to already be in the root directory. If we needed
+//    to preserve sub paths then we might want to zip the files first and then
+//    unzip them below the new parent directory.
+//  - the path names "res/" and "testres/" and duplicated in .java source files
+//    (DefaultMimeMapFactory.java and MimeMapTest.java, as of October 2019).
+java_genrule {
+    name: "mimemap-res.jar",
+    tools: [
+        "soong_zip",
+    ],
+    srcs: [":mime.types"],
+    out: ["mimemap-res.jar"],
+    cmd: "mkdir $(genDir)/res/ && cp $(in) $(genDir)/res/ && $(location soong_zip) -C $(genDir) -o $(out) -D $(genDir)/res/",
+}
 
-    srcs: [
-        "java/android/content/type/DefaultMimeMapFactory.java",
+// The same as mimemap-res.jar except that the resources are placed in a different directory.
+// They get bundled with CTS so that CTS can compare a device's MimeMap implementation vs.
+// the stock Android one from when CTS was built.
+java_genrule {
+    name: "mimemap-testing-res.jar",
+    tools: [
+        "soong_zip",
     ],
+    srcs: [":mime.types"],
+    out: ["mimemap-testing-res.jar"],
+    cmd: "mkdir $(genDir)/testres/ && cp $(in) $(genDir)/testres/ && $(location soong_zip) -C $(genDir) -o $(out) -D $(genDir)/testres/",
+}
 
-    java_resources: [
+// Combination of all *mime.types resources.
+filegroup {
+    name: "mime.types",
+    visibility: [
+        "//visibility:private",
+    ],
+    srcs: [
         ":debian.mime.types",
         ":android.mime.types",
         ":vendor.mime.types",
     ],
-
-    sdk_version: "core_platform",
 }
 
 filegroup {
diff --git a/mime/jarjar-rules.txt b/mime/jarjar-rules.txt
new file mode 100644
index 000000000000..145d1dbf3d11
--- /dev/null
+++ b/mime/jarjar-rules.txt
@@ -0,0 +1 @@
+rule android.content.type.DefaultMimeMapFactory android.content.type.cts.StockAndroidMimeMapFactory
\ No newline at end of file
diff --git a/mime/java/android/content/type/DefaultMimeMapFactory.java b/mime/java/android/content/type/DefaultMimeMapFactory.java
index 56b234fe0e1c..13039a4ab1e2 100644
--- a/mime/java/android/content/type/DefaultMimeMapFactory.java
+++ b/mime/java/android/content/type/DefaultMimeMapFactory.java
@@ -20,10 +20,13 @@ import libcore.net.MimeMap;
 
 import java.io.BufferedReader;
 import java.io.IOException;
+import java.io.InputStream;
 import java.io.InputStreamReader;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.List;
+import java.util.Objects;
+import java.util.function.Function;
 import java.util.regex.Pattern;
 
 /**
@@ -45,21 +48,33 @@ public class DefaultMimeMapFactory {
      * Android's default mapping between MIME types and extensions.
      */
     public static MimeMap create() {
-        MimeMap.Builder builder = MimeMap.builder();
-        parseTypes(builder, true, "/mime.types");
-        parseTypes(builder, true, "/android.mime.types");
-        parseTypes(builder, false, "/vendor.mime.types");
-        return builder.build();
+        Class c = DefaultMimeMapFactory.class;
+        // The resources are placed into the res/ path by the "mimemap-res.jar" genrule.
+        return create(resourceName -> c.getResourceAsStream("/res/" + resourceName));
     }
 
     private static final Pattern SPLIT_PATTERN = Pattern.compile("\\s+");
 
+    /**
+     * Creates a {@link MimeMap} instance whose resources are loaded from the
+     * InputStreams looked up in {@code resourceSupplier}.
+     *
+     * @hide
+     */
+    public static MimeMap create(Function<String, InputStream> resourceSupplier) {
+        MimeMap.Builder builder = MimeMap.builder();
+        parseTypes(builder, true, resourceSupplier, "mime.types");
+        parseTypes(builder, true, resourceSupplier, "android.mime.types");
+        parseTypes(builder, false, resourceSupplier, "vendor.mime.types");
+        return builder.build();
+    }
+
     private static void parseTypes(MimeMap.Builder builder, boolean allowOverwrite,
-            String resource) {
-        try (BufferedReader r = new BufferedReader(
-                new InputStreamReader(DefaultMimeMapFactory.class.getResourceAsStream(resource)))) {
+            Function<String, InputStream> resourceSupplier, String resourceName) {
+        try (InputStream inputStream = Objects.requireNonNull(resourceSupplier.apply(resourceName));
+             BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream))) {
             String line;
-            while ((line = r.readLine()) != null) {
+            while ((line = reader.readLine()) != null) {
                 int commentPos = line.indexOf('#');
                 if (commentPos >= 0) {
                     line = line.substring(0, commentPos);
@@ -78,7 +93,7 @@ public class DefaultMimeMapFactory {
                 builder.put(specs.get(0), specs.subList(1, specs.size()));
             }
         } catch (IOException | RuntimeException e) {
-            throw new RuntimeException("Failed to parse " + resource, e);
+            throw new RuntimeException("Failed to parse " + resourceName, e);
         }
     }