JsonSchemaCompiler: Ensure we never concatenate different errors.

After https://chromium-review.googlesource.com/c/chromium/src/+/2519173,
we raise a hard error on failing to parse optional properties. As a
result, we should never be concatenating unrelated errors. Modify the
code to reflect the same.

BUG=1113513

Change-Id: If7a4220435378207d84e32e9dd093d63059e7a29
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2547422Reviewed-by: Devlin <rdevlin.cronin@chromium.org>
Commit-Queue: Karan Bhatia <karandeepb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#828993}

tools/json_schema_compiler/cc_generator.py

@@ -1274,9 +1274,8 @@ class _Generator(object):
     c = Code()
     if not self._generate_error_messages:
       return c
-    (c.Append('if (error->length())')
-      .Append('  error->append(UTF8ToUTF16("; "));')
-      .Append('error->append(%s);' % error16))
+    c.Append('DCHECK(error->empty());')
+    c.Append('*error = %s;' % error16)
     return c
 
   def _GenerateError(self, body):

tools/json_schema_compiler/manifest_parse_util.cc

@@ -46,6 +46,7 @@ void PopulateInvalidEnumValueError(
     base::string16* error,
     std::vector<base::StringPiece>* error_path_reversed) {
   DCHECK(error);
+  DCHECK(error->empty());
   DCHECK(error_path_reversed);
   DCHECK(error_path_reversed->empty());
 
@@ -76,6 +77,7 @@ const base::Value* FindKeyOfType(
     base::string16* error,
     std::vector<base::StringPiece>* error_path_reversed) {
   DCHECK(error);
+  DCHECK(error->empty());
   DCHECK(error_path_reversed);
   DCHECK(error_path_reversed->empty());
 

tools/json_schema_compiler/test/error_generation_unittest.cc

@@ -309,25 +309,6 @@ TEST(JsonSchemaCompilerErrorTest, OptionalUnableToPopulateArray) {
   }
 }
 
-TEST(JsonSchemaCompilerErrorTest, MultiplePopulationErrors) {
-  {
-    std::unique_ptr<base::DictionaryValue> value =
-        Dictionary("TheArray", std::make_unique<Value>(5));
-    errors::ArrayObject out;
-    base::string16 error;
-    EXPECT_FALSE(errors::ArrayObject::Populate(*value, &out, &error));
-    EXPECT_TRUE(EqualsUtf16("'TheArray': expected list, got integer",
-        error));
-    EXPECT_EQ(NULL, out.the_array.get());
-
-    EXPECT_FALSE(errors::ArrayObject::Populate(*value, &out, &error));
-    EXPECT_TRUE(EqualsUtf16("'TheArray': expected list, got integer; "
-        "'TheArray': expected list, got integer",
-        error));
-    EXPECT_EQ(NULL, out.the_array.get());
-  }
-}
-
 TEST(JsonSchemaCompilerErrorTest, TooManyKeys) {
   {
     std::unique_ptr<base::DictionaryValue> value =

tools/json_schema_compiler/util.cc

@@ -16,11 +16,10 @@ namespace {
 bool ReportError(const base::Value& from,
                  base::Value::Type expected,
                  base::string16* error) {
-  if (!error->empty())
-    error->append(base::ASCIIToUTF16("; "));
-  error->append(base::ASCIIToUTF16(base::StringPrintf(
+  DCHECK(error->empty());
+  *error = base::ASCIIToUTF16(base::StringPrintf(
       "expected %s, got %s", base::Value::GetTypeName(expected),
-      base::Value::GetTypeName(from.type()))));
+      base::Value::GetTypeName(from.type())));
   return false;  // Always false on purpose.
 }
 

tools/json_schema_compiler/util.h

@@ -95,11 +95,10 @@ bool PopulateArrayFromList(const base::ListValue& list_value,
   const auto& list = list_value.GetList();
   for (size_t i = 0; i < list.size(); ++i) {
     if (!PopulateItem(list[i], &item, &item_error)) {
-      if (!error->empty())
-        error->append(base::ASCIIToUTF16("; "));
-      error->append(base::ASCIIToUTF16(
+      DCHECK(error->empty());
+      *error = base::ASCIIToUTF16(
           base::StringPrintf("Parsing array failed at index %" PRIuS ": %s", i,
-                             base::UTF16ToASCII(item_error).c_str())));
+                             base::UTF16ToASCII(item_error).c_str()));
       return false;
     }
     out->push_back(std::move(item));