[clang-format] Add option to specify explicit config file

[gigadude]

Summary

This diff extends the -style=file option to allow a config file to be specified explicitly. This is useful (for instance) when adding IDE commands to reformat code to a personal style.

Usage:

clang-format -style=file:<configfilepath> ...

[djasper]

lib/Format/Format.cpp

2017

I think not finding the config file should be an error.

[gigadude]

Return a "Config file <name> not found" error if the file: style's file isn't found.

[alexfh]

Please add a test for the new -style syntax.

[gigadude]

@alexfh do you mean to the clang-format-test.el file (which I don't know how to run) or to the FormatTests? If the latter would the right place be TEST(FormatStyle, GetStyleOfFile)?

[gigadude]

Add FormatTest for style=file:<path>

[ioeric]

The patch has "Context not available" issue (i.e. I couldn't expand to see code around the changes). Could you re-upload the diff?

lib/Format/Format.cpp

1966

Could you also update the comment in include/clang/Format/Format.h?

2027

I think the logic of parsing config files should be similar in the "--style=file" case. Could you pull it into a function to avoid duplication?

[alexfh]

Please re-upload the patch with the full context (see http://llvm.org/docs/Phabricator.html).

[krasimir]

unittests/Format/FormatTest.cpp

10429

Please also add tests for what's the expected behavior with relative paths.

lib/Format/Format.cpp

     ".clang-format file located in one of the parent\n"
     "directories of the source file (or current\n"
     "directory for stdin).\n"
+    "Use -style=file:<configfile> to explicitly specify\n"
+    "the configuration file.\n"
     "Use -style=\"{key: value, ...}\" to set specific\n"
     "parameters, e.g.:\n"
     "  -style=\"{BasedOnStyle: llvm, IndentWidth: 8}\"";

     return Style;
   }
 
+  // Check for explicit config filename
+  if (StyleName.startswith_lower("file:")) {
+    SmallString<128> ConfigFile(StyleName.substr(5));
+    auto Status = FS->status(ConfigFile.str());
+    bool FoundConfigFile =
+        Status && (Status->getType() == llvm::sys::fs::file_type::regular_file);
+    if (!FoundConfigFile) {
+      return make_string_error("Configuration file " + ConfigFile + " not found");
+    }
+    llvm::ErrorOr<std::unique_ptr<llvm::MemoryBuffer>> Text =
+        FS->getBufferForFile(ConfigFile.str());
+    if (std::error_code EC = Text.getError())
+      return make_string_error(EC.message());
+    if (std::error_code ec = parseConfiguration(Text.get()->getBuffer(), &Style)) {
+      if (ec == ParseError::Unsuitable) {
+        return make_string_error("Configuration file " + ConfigFile +
+          " does not support " + getLanguageName(Style.Language));
+      }
+      return make_string_error("Error reading " + ConfigFile + ": " + ec.message());
+    }
+    DEBUG(llvm::dbgs() << "Using configuration file " << ConfigFile << "\n");
+    return Style;
+  }
+
   if (!StyleName.equals_lower("file")) {
     if (!getPredefinedStyle(StyleName, Style.Language, &Style))
       return make_string_error("Invalid value for -style");

unittests/Format/FormatTest.cpp

   auto Style7 = getStyle("file", "/d/.clang-format", "LLVM", "", &FS);
   ASSERT_FALSE((bool)Style7);
   llvm::consumeError(Style7.takeError());
+
+  // Test 8: explicit format file in parent directory.
+  ASSERT_TRUE(
+      FS.addFile("/e/.clang-format", 0,
+                 llvm::MemoryBuffer::getMemBuffer("BasedOnStyle: LLVM")));
+  ASSERT_TRUE(
+      FS.addFile("/e/explicit.clang-format", 0,
+                 llvm::MemoryBuffer::getMemBuffer("BasedOnStyle: Google")));
+  ASSERT_TRUE(FS.addFile("/e/sub/sub/sub/test.cpp", 0,
+                         llvm::MemoryBuffer::getMemBuffer("int i;")));
+  auto Style8 = getStyle("file:/e/explicit.clang-format", "/e/sub/sub/sub/test.cpp", "LLVM", "", &FS);
+  ASSERT_TRUE((bool)Style8);
+  ASSERT_EQ(*Style8, getGoogleStyle());
+
+  // Test 9: missing explicit format file
+  auto Style9 = getStyle("file:/e/missing.clang-format", "/e/sub/sub/sub/test.cpp", "LLVM", "", &FS);
+  ASSERT_FALSE((bool)Style9);
+  llvm::consumeError(Style9.takeError());
 }
 
 TEST_F(ReplacementTest, FormatCodeAfterReplacements) {