[clang-format] Add --fail-on-incomplete-format. (llvm#84346)

At the moment clang-format will return exit code 0 on incomplete
results. In scripts it would sometimes be useful if clang-format would
instead fail in those cases, signalling that there was something wrong
with the code being formatted.

---------

Co-authored-by: Björn Schäpers <[email protected]>
Co-authored-by: Owen Pan <[email protected]>

Author: 3 people

clang/docs/ClangFormat.rst

@@ -61,6 +61,7 @@ to format C/C++/Java/JavaScript/JSON/Objective-C/Protobuf/C# code.
     --dry-run                      - If set, do not actually make the formatting changes
     --dump-config                  - Dump configuration options to stdout and exit.
                                      Can be used with -style option.
+    --fail-on-incomplete-format    - If set, fail with exit code 1 on incomplete format.
     --fallback-style=<string>      - The name of the predefined style used as a
                                      fallback in case clang-format is invoked with
                                      -style=file, but can not find the .clang-format

clang/test/Format/fail-on-incomplete.cpp

@@ -0,0 +1,4 @@
+// RUN: not clang-format -style=LLVM -fail-on-incomplete-format %s
+// RUN: clang-format -style=LLVM %s
+
+int a(

clang/tools/clang-format/ClangFormat.cpp

@@ -205,6 +205,11 @@ static cl::list<std::string> FileNames(cl::Positional,
                                        cl::desc("[@<file>] [<file> ...]"),
                                        cl::cat(ClangFormatCategory));
 
+static cl::opt<bool> FailOnIncompleteFormat(
+    "fail-on-incomplete-format",
+    cl::desc("If set, fail with exit code 1 on incomplete format."),
+    cl::init(false), cl::cat(ClangFormatCategory));
+
 namespace clang {
 namespace format {
 
@@ -399,7 +404,7 @@ class ClangFormatDiagConsumer : public DiagnosticConsumer {
 };
 
 // Returns true on error.
-static bool format(StringRef FileName) {
+static bool format(StringRef FileName, bool ErrorOnIncompleteFormat = false) {
   const bool IsSTDIN = FileName == "-";
   if (!OutputXML && Inplace && IsSTDIN) {
     errs() << "error: cannot use -i when reading from stdin.\n";
@@ -535,7 +540,7 @@ static bool format(StringRef FileName) {
       Rewrite.getEditBuffer(ID).write(outs());
     }
   }
-  return false;
+  return ErrorOnIncompleteFormat && !Status.FormatComplete;
 }
 
 } // namespace format
@@ -699,7 +704,7 @@ int main(int argc, const char **argv) {
   }
 
   if (FileNames.empty())
-    return clang::format::format("-");
+    return clang::format::format("-", FailOnIncompleteFormat);
 
   if (FileNames.size() > 1 &&
       (!Offsets.empty() || !Lengths.empty() || !LineRanges.empty())) {
@@ -717,7 +722,7 @@ int main(int argc, const char **argv) {
       errs() << "Formatting [" << FileNo++ << "/" << FileNames.size() << "] "
              << FileName << "\n";
     }
-    Error |= clang::format::format(FileName);
+    Error |= clang::format::format(FileName, FailOnIncompleteFormat);
   }
   return Error ? 1 : 0;
 }