Bug 1904747 - Do not report error or warning in JS_Utf8BufferIsCompilableUnit. r=bthrall

Differential Revision: https://phabricator.services.mozilla.com/D214913

js/public/CompilationAndEvaluation.h

@@ -45,8 +45,8 @@ class SourceText;
  * lines in a buffer until JS_Utf8BufferIsCompilableUnit is true, then pass it
  * to the compiler.
  *
- * The provided buffer is interpreted as UTF-8 data.  An error is reported if
- * a UTF-8 encoding error is encountered.
+ * The provided buffer is interpreted as UTF-8 data.  If a UTF-8 encoding error
+ * is encountered, reports an error to JSContext and returns *true*.
  */
 extern JS_PUBLIC_API bool JS_Utf8BufferIsCompilableUnit(
     JSContext* cx, JS::Handle<JSObject*> obj, const char* utf8, size_t length);

js/src/jsapi-tests/moz.build

@@ -79,6 +79,7 @@ UNIFIED_SOURCES += [
     "testIntern.cpp",
     "testIntlAvailableLocales.cpp",
     "testIntString.cpp",
+    "testIsCompilableUnit.cpp",
     "testIsInsideNursery.cpp",
     "testIsISOStyleDate.cpp",
     "testIteratorObject.cpp",

js/src/jsapi-tests/testIsCompilableUnit.cpp

@@ -0,0 +1,69 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "mozilla/Utf8.h"  // mozilla::Utf8Unit
+
+#include <string_view>
+
+#include "js/CompilationAndEvaluation.h"  // JS_Utf8BufferIsCompilableUnit
+#include "js/ErrorReport.h"               // JSErrorReport
+#include "js/GlobalObject.h"              // JS::CurrentGlobalOrNull
+#include "js/RootingAPI.h"                // JS::Rooted
+#include "js/SourceText.h"                // JS::SourceText, JS::SourceOwnership
+#include "js/Warnings.h"                  // JS::SetWarningReporter
+#include "jsapi-tests/tests.h"
+
+static bool gIsCompilableUnitWarned = false;
+
+BEGIN_TEST(testIsCompilableUnit) {
+  JS::SetWarningReporter(cx, WarningReporter);
+
+  // Compilable case.
+  {
+    static constexpr std::string_view src = "1";
+    CHECK(JS_Utf8BufferIsCompilableUnit(cx, global, src.data(), src.length()));
+    CHECK(!JS_IsExceptionPending(cx));
+    CHECK(!gIsCompilableUnitWarned);
+  }
+
+  // Not compilable cases.
+  {
+    static constexpr std::string_view src = "1 + ";
+    CHECK(!JS_Utf8BufferIsCompilableUnit(cx, global, src.data(), src.length()));
+    CHECK(!JS_IsExceptionPending(cx));
+    CHECK(!gIsCompilableUnitWarned);
+  }
+
+  {
+    static constexpr std::string_view src = "() =>";
+    CHECK(!JS_Utf8BufferIsCompilableUnit(cx, global, src.data(), src.length()));
+    CHECK(!JS_IsExceptionPending(cx));
+    CHECK(!gIsCompilableUnitWarned);
+  }
+
+  // Compilable but warned case.
+  {
+    static constexpr std::string_view src = "() => { return; unreachable(); }";
+    CHECK(JS_Utf8BufferIsCompilableUnit(cx, global, src.data(), src.length()));
+    CHECK(!JS_IsExceptionPending(cx));
+    CHECK(!gIsCompilableUnitWarned);
+  }
+
+  // Invalid UTF-8 case.
+  // This should report error with returning *true*.
+  {
+    static constexpr std::string_view src = "\x80";
+    CHECK(JS_Utf8BufferIsCompilableUnit(cx, global, src.data(), src.length()));
+    CHECK(JS_IsExceptionPending(cx));
+    CHECK(!gIsCompilableUnitWarned);
+    JS_ClearPendingException(cx);
+  }
+
+  return true;
+}
+
+static void WarningReporter(JSContext* cx, JSErrorReport* report) {
+  gIsCompilableUnitWarned = true;
+}
+END_TEST(testIsCompilableUnit);

js/src/vm/CompilationAndEvaluation.cpp

@@ -184,10 +184,6 @@ JS_PUBLIC_API bool JS_Utf8BufferIsCompilableUnit(JSContext* cx,
     return true;
   }
 
-  // Return true on any out-of-memory error or non-EOF-related syntax error, so
-  // our caller doesn't try to collect more buffered source.
-  bool result = true;
-
   using frontend::FullParseHandler;
   using frontend::ParseGoal;
   using frontend::Parser;
@@ -208,6 +204,9 @@ JS_PUBLIC_API bool JS_Utf8BufferIsCompilableUnit(JSContext* cx,
     return false;
   }
 
+  // Warnings and errors during parsing shouldn't be reported.
+  fc.clearAutoReport();
+
   Parser<FullParseHandler, char16_t> parser(&fc, options, chars.get(), length,
                                             /* foldConstants = */ true,
                                             compilationState,
@@ -217,13 +216,13 @@ JS_PUBLIC_API bool JS_Utf8BufferIsCompilableUnit(JSContext* cx,
     // return false so our caller knows to try to collect more buffered
     // source.
     if (parser.isUnexpectedEOF()) {
-      result = false;
+      return false;
     }
-
-    cx->clearPendingException();
   }
 
-  return result;
+  // Return true on any out-of-memory error or non-EOF-related syntax error, so
+  // our caller doesn't try to collect more buffered source.
+  return true;
 }
 
 class FunctionCompiler {