tools: add make format-cpp to run clang-format on C++ diffs

This patch adds a `make format-cpp` shortcut to the Makefile
that runs clang-format on the C++ diffs, and a
`make format-cpp-build` to install clang-format from
npm.

To format staged changes:

```
$ make format-cpp
```

To format HEAD~1...HEAD (latest commit):

```
$ CLANG_FORMAT_START=`git rev-parse HEAD~1` make format-cpp
```

To format diff between master and current branch head (master...HEAD):

```
$ CLANG_FORMAT_START=master make format-cpp
```

Most of the .clang-format file comes from running

```
$ clang-format --dump-config --style=Google
```

with clang-format built with llvm/trunk 328768 (npm version 1.2.3)

The clang-format version is fixed because different version of
clang-format may format the files differently.

PR-URL: #21997
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Gus Caplan <me@gus.host>
Reviewed-By: Michaël Zasso <targos@protonmail.com>

.clang-format

@@ -0,0 +1,111 @@
+---
+Language:        Cpp
+# BasedOnStyle:  Google
+AccessModifierOffset: -1
+AlignAfterOpenBracket: Align
+AlignConsecutiveAssignments: false
+AlignConsecutiveDeclarations: false
+AlignEscapedNewlines: Right
+AlignOperands:   true
+AlignTrailingComments: true
+AllowAllParametersOfDeclarationOnNextLine: true
+AllowShortBlocksOnASingleLine: false
+AllowShortCaseLabelsOnASingleLine: false
+AllowShortFunctionsOnASingleLine: Inline
+AllowShortIfStatementsOnASingleLine: true
+AllowShortLoopsOnASingleLine: true
+AlwaysBreakAfterDefinitionReturnType: None
+AlwaysBreakAfterReturnType: None
+AlwaysBreakBeforeMultilineStrings: false
+AlwaysBreakTemplateDeclarations: true
+BinPackArguments: false
+BinPackParameters: false
+BraceWrapping:
+  AfterClass:      false
+  AfterControlStatement: false
+  AfterEnum:       false
+  AfterFunction:   false
+  AfterNamespace:  false
+  AfterObjCDeclaration: false
+  AfterStruct:     false
+  AfterUnion:      false
+  AfterExternBlock: false
+  BeforeCatch:     false
+  BeforeElse:      false
+  IndentBraces:    false
+  SplitEmptyFunction: true
+  SplitEmptyRecord: true
+  SplitEmptyNamespace: true
+BreakBeforeBinaryOperators: None
+BreakBeforeBraces: Attach
+BreakBeforeInheritanceComma: false
+BreakBeforeTernaryOperators: true
+BreakConstructorInitializersBeforeComma: false
+BreakConstructorInitializers: BeforeColon
+BreakAfterJavaFieldAnnotations: false
+BreakStringLiterals: true
+ColumnLimit:      80
+CommentPragmas:  '^ IWYU pragma:'
+CompactNamespaces: false
+ConstructorInitializerAllOnOneLineOrOnePerLine: true
+ConstructorInitializerIndentWidth: 4
+ContinuationIndentWidth: 4
+Cpp11BracedListStyle: true
+DerivePointerAlignment: false
+DisableFormat:   false
+ExperimentalAutoDetectBinPacking: false
+FixNamespaceComments: true
+ForEachMacros:
+  - foreach
+  - Q_FOREACH
+  - BOOST_FOREACH
+IncludeBlocks:   Preserve
+IncludeCategories:
+  - Regex:           '^<ext/.*\.h>'
+    Priority:        2
+  - Regex:           '^<.*\.h>'
+    Priority:        1
+  - Regex:           '^<.*'
+    Priority:        2
+  - Regex:           '.*'
+    Priority:        3
+IncludeIsMainRegex: '([-_](test|unittest))?$'
+IndentCaseLabels: true
+IndentPPDirectives: None
+IndentWidth:     2
+IndentWrappedFunctionNames: false
+JavaScriptQuotes: Leave
+JavaScriptWrapImports: true
+KeepEmptyLinesAtTheStartOfBlocks: false
+MacroBlockBegin: ''
+MacroBlockEnd:   ''
+MaxEmptyLinesToKeep: 1
+NamespaceIndentation: None
+ObjCBlockIndentWidth: 2
+ObjCSpaceAfterProperty: false
+ObjCSpaceBeforeProtocolList: false
+PenaltyBreakAssignment: 2
+PenaltyBreakBeforeFirstCallParameter: 1
+PenaltyBreakComment: 300
+PenaltyBreakFirstLessLess: 120
+PenaltyBreakString: 1000
+PenaltyExcessCharacter: 1000000
+PenaltyReturnTypeOnItsOwnLine: 200
+PointerAlignment: Left
+ReflowComments:  true
+SortIncludes:    true
+SortUsingDeclarations: true
+SpaceAfterCStyleCast: false
+SpaceAfterTemplateKeyword: true
+SpaceBeforeAssignmentOperators: true
+SpaceBeforeParens: ControlStatements
+SpaceInEmptyParentheses: false
+SpacesBeforeTrailingComments: 2
+SpacesInAngles:  false
+SpacesInContainerLiterals: true
+SpacesInCStyleCastParentheses: false
+SpacesInParentheses: false
+SpacesInSquareBrackets: false
+Standard:        Auto
+TabWidth:        8
+UseTab:          Never

.gitignore

@@ -4,6 +4,7 @@
 !test/fixtures/**/.*
 !tools/node_modules/**/.*
 !tools/doc/node_modules/**/.*
+!.clang-format
 !.editorconfig
 !.eslintignore
 !.eslintrc.js

Makefile

@@ -1169,6 +1169,33 @@ LINT_CPP_FILES = $(filter-out $(LINT_CPP_EXCLUDE), $(wildcard \
 # and the actual filename is generated so it won't match header guards
 ADDON_DOC_LINT_FLAGS=-whitespace/ending_newline,-build/header_guard
 
+format-cpp-build:
+	cd tools/clang-format && $(call available-node,$(run-npm-install))
+
+format-cpp-clean:
+	$(RM) -r tools/clang-format/node_modules
+
+CLANG_FORMAT_START ?= HEAD
+.PHONY: format-cpp
+# To format staged changes:
+#  $ make format-cpp
+# To format HEAD~1...HEAD (latest commit):
+#  $ CLANG_FORMAT_START=`git rev-parse HEAD~1` make format-cpp
+# To format diff between master and current branch head (master...HEAD):
+#  $ CLANG_FORMAT_START=master make format-cpp
+format-cpp: ## Format C++ diff from $CLANG_FORMAT_START to current changes
+ifneq ("","$(wildcard tools/clang-format/node_modules/)")
+	@echo "Formatting C++ diff from $(CLANG_FORMAT_START).."
+	@$(PYTHON) tools/clang-format/node_modules/.bin/git-clang-format \
+		--binary=tools/clang-format/node_modules/.bin/clang-format \
+		--style=file \
+		$(CLANG_FORMAT_START) -- \
+		$(LINT_CPP_FILES)
+else
+	@echo "clang-format is not installed."
+	@echo "To install (requires internet access) run: $ make format-cpp-build"
+endif
+
 .PHONY: lint-cpp
 # Lints the C++ code with cpplint.py and check-imports.py.
 lint-cpp: tools/.cpplintstamp

tools/clang-format/package.json

@@ -0,0 +1,9 @@
+{
+  "name": "node-core-clang-format",
+  "version": "1.0.0",
+  "description": "Formatting C++ files for Node.js core",
+  "license": "MIT",
+  "dependencies": {
+    "clang-format": "1.2.3"
+  }
+}