Block usage of handle<shared_buffer> in Chrome mojom files.

Chrome Mojo interfaces should prefer one of the higher-level primitives
built on top of the native Mojo handle<shared_buffer>:

- mojo_base.mojom.ReadOnlySharedMemoryRegion
- mojo_base.mojom.WritableSharedMemoryRegion
- mojo_base.mojom.UnsafeSharedMemoryRegion

Fixed: 1132241
Change-Id: I082d512594db6cedb9146928e40f7387a492bbe2
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3526187
Reviewed-by: Robert Sesek <rsesek@chromium.org>
Commit-Queue: Daniel Cheng <dcheng@chromium.org>
Cr-Commit-Position: refs/heads/main@{#981728}

PRESUBMIT.py

@@ -126,7 +126,6 @@ class BanRule:
   excluded_paths: Optional[Sequence[str]] = None
 
 
-# Format: Sequence of BanRule:
 _BANNED_JAVA_IMPORTS : Sequence[BanRule] = (
     BanRule(
       'import java.net.URI;',
@@ -175,7 +174,6 @@ class BanRule:
     ),
 )
 
-# Format: Sequence of BanRule:
 _BANNED_JAVA_FUNCTIONS : Sequence[BanRule] = (
     BanRule(
       'StrictMode.allowThreadDiskReads()',
@@ -203,7 +201,6 @@ class BanRule:
     ),
 )
 
-# Format: Sequence of BanRule:
 _BANNED_OBJC_FUNCTIONS : Sequence[BanRule] = (
     BanRule(
       'addTrackingRect:',
@@ -305,7 +302,6 @@ class BanRule:
     ),
 )
 
-# Format: Sequence of BanRule:
 _BANNED_IOS_OBJC_FUNCTIONS = (
     BanRule(
       r'/\bTEST[(]',
@@ -328,7 +324,6 @@ class BanRule:
     ),
 )
 
-# Format: Sequence of BanRule:
 _BANNED_IOS_EGTEST_FUNCTIONS : Sequence[BanRule] = (
     BanRule(
       r'/\bEXPECT_OCMOCK_VERIFY\b',
@@ -340,7 +335,6 @@ class BanRule:
     ),
 )
 
-# Format: Sequence of BanRule:
 _BANNED_CPP_FUNCTIONS : Sequence[BanRule] = (
     BanRule(
       r'/\busing namespace ',
@@ -1008,6 +1002,19 @@ class BanRule:
     ),
 )
 
+_BANNED_MOJOM_PATTERNS : Sequence[BanRule] = (
+    BanRule(
+        'handle<shared_buffer>',
+        (
+         'Please use one of the more specific shared memory types instead:',
+         '  mojo_base.mojom.ReadOnlySharedMemoryRegion',
+         '  mojo_base.mojom.WritableSharedMemoryRegion',
+         '  mojo_base.mojom.UnsafeSharedMemoryRegion',
+        ),
+        True,
+    ),
+)
+
 # Format: Sequence of tuples containing:
 # * String pattern or, if starting with a slash, a regular expression.
 # * Sequence of strings to show when the pattern matches.
@@ -1683,6 +1690,13 @@ def CheckForMatch(affected_file, line_num: int, line: str,
             for ban_rule in _BANNED_CPP_FUNCTIONS:
                 CheckForMatch(f, line_num, line, ban_rule)
 
+    file_filter = lambda f: f.LocalPath().endswith(('.mojom'))
+    for f in input_api.AffectedFiles(file_filter=file_filter):
+        for line_num, line in f.ChangedContents():
+            for ban_rule in _BANNED_MOJOM_PATTERNS:
+                CheckForMatch(f, line_num, line, ban_rule)
+
+
     result = []
     if (warnings):
         result.append(

PRESUBMIT_test.py

@@ -2591,6 +2591,28 @@ def testBannedMojoFunctions(self):
     self.assertTrue('third_party/blink/ok/file3.cc' not in results[0].message)
     self.assertTrue('content/renderer/ok/file3.cc' not in results[0].message)
 
+  def testBannedMojomPatterns(self):
+    input_api = MockInputApi()
+    input_api.files = [
+      MockFile('bad.mojom',
+               ['struct Bad {',
+                '  handle<shared_buffer> buffer;',
+                '};']),
+      MockFile('good.mojom',
+               ['struct  Good {',
+                '  mojo_base.mojom.ReadOnlySharedMemoryRegion region1;',
+                '  mojo_base.mojom.WritableSharedMemoryRegion region2;',
+                '  mojo_base.mojom.UnsafeSharedMemoryRegion region3;',
+                '};']),
+    ]
+
+    results = PRESUBMIT.CheckNoBannedFunctions(input_api, MockOutputApi())
+
+    # warnings are results[0], errors are results[1]
+    self.assertEqual(1, len(results))
+    self.assertTrue('bad.mojom' in results[0].message)
+    self.assertTrue('good.mojom' not in results[0].message)
+
   def testDeprecatedMojoTypes(self):
     ok_paths = ['components/arc']
     warning_paths = ['some/cpp']