[clang-format] Handle raw string literals containing JSON code

Fix #65400

clang/lib/Format/Format.cpp

@@ -3808,8 +3808,10 @@ reformat(const FormatStyle &Style, StringRef Code,
     tooling::Replacements Replaces =
         Formatter(*Env, Style, Status).process().first;
     // add a replacement to remove the "x = " from the result.
-    Replaces = Replaces.merge(
-        tooling::Replacements(tooling::Replacement(FileName, 0, 4, "")));
+    if (Code.starts_with("x = ")) {
+      Replaces = Replaces.merge(
+          tooling::Replacements(tooling::Replacement(FileName, 0, 4, "")));
+    }
     // apply the reformatting changes and the removal of "x = ".
     if (applyAllReplacements(Code, Replaces))
       return {Replaces, 0};

clang/tools/clang-format/ClangFormat.cpp

@@ -491,8 +491,8 @@ static bool format(StringRef FileName, bool ErrorOnIncompleteFormat = false) {
   // To format JSON insert a variable to trick the code into thinking its
   // JavaScript.
   if (IsJson && !FormatStyle->DisableFormat) {
-    auto Err = Replaces.add(tooling::Replacement(
-        tooling::Replacement(AssumedFileName, 0, 0, "x = ")));
+    auto Err =
+        Replaces.add(tooling::Replacement(AssumedFileName, 0, 0, "x = "));
     if (Err)
       llvm::errs() << "Bad Json variable insertion\n";
   }

clang/unittests/Format/FormatTestRawStrings.cpp

@@ -988,6 +988,28 @@ fffffffffffffffffffff("aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa",
                       )pb");)test",
                    Style));
 }
+
+TEST_F(FormatTestRawStrings, Json) {
+  auto Style = getLLVMStyle();
+  Style.RawStringFormats = {
+      {
+          /*Language=*/FormatStyle::LK_Json,
+          /*Delimiters=*/{"json"},
+          /*EnclosingFunctions=*/{},
+          /*CanonicalDelimiter=*/"",
+          /*BasedOnStyle=*/"llvm",
+      },
+  };
+
+  EXPECT_EQ(R"test(json = R"json({
+                "str": "test"
+              })json";)test",
+            format(R"test(json = R"json({
+  "str": "test"
+})json";)test",
+                   Style));
+}
+
 } // end namespace
 } // end namespace format
 } // end namespace clang