clang-format: [JS] options for arrow functions.

Summary:
clang-format currently always wraps the body of non-empty arrow
functions:

    const x = () => {
      z();
    };

This change implements support for the `AllowShortLambdasOnASingleLine`
style options, controlling the indent style for arrow function bodies
that have one or fewer statements. SLS_All puts all on a single line,
SLS_Inline only arrow functions used in an inline position.

    const x = () => { z(); };

Multi-statement arrow functions continue to be wrapped. Function
expressions (`a = function() {}`) and function/method declarations are
unaffected as well.

Reviewers: krasimir

Subscribers: cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D73335

diff --git a/clang/lib/Format/Format.cpp b/clang/lib/Format/Format.cpp
index a962e32..bc95517 100644 (file)
--- a/clang/lib/Format/Format.cpp
+++ b/clang/lib/Format/Format.cpp
@@ -939,6 +939,8 @@ FormatStyle getGoogleStyle(FormatStyle::LanguageKind Language) {
     GoogleStyle.AlignAfterOpenBracket = FormatStyle::BAS_AlwaysBreak;
     GoogleStyle.AlignOperands = false;
     GoogleStyle.AllowShortFunctionsOnASingleLine = FormatStyle::SFS_Empty;
+    // TODO: still under discussion whether to switch to SLS_All.
+    GoogleStyle.AllowShortLambdasOnASingleLine = FormatStyle::SLS_Empty;
     GoogleStyle.AlwaysBreakBeforeMultilineStrings = false;
     GoogleStyle.BreakBeforeTernaryOperators = false;
     // taze:, triple slash directives (`/// <...`), tslint:, and @see, which is

diff --git a/clang/lib/Format/TokenAnnotator.cpp b/clang/lib/Format/TokenAnnotator.cpp
index 723dc5c..8f9a29a 100644 (file)
--- a/clang/lib/Format/TokenAnnotator.cpp
+++ b/clang/lib/Format/TokenAnnotator.cpp
@@ -3144,6 +3144,26 @@ bool TokenAnnotator::mustBreakBefore(const AnnotatedLine &Line,
       // JavaScript top-level enum key/value pairs are put on separate lines
       // instead of bin-packing.
       return true;
+    if (Right.is(tok::r_brace) && Left.is(tok::l_brace) && Left.Previous &&
+        Left.Previous->is(TT_JsFatArrow)) {
+      // JS arrow function (=> {...}).
+      switch (Style.AllowShortLambdasOnASingleLine) {
+      case FormatStyle::SLS_All:
+        return false;
+      case FormatStyle::SLS_None:
+        return true;
+      case FormatStyle::SLS_Empty:
+        return !Left.Children.empty();
+      case FormatStyle::SLS_Inline:
+        // allow one-lining inline (e.g. in function call args) and empty arrow
+        // functions.
+        return (Left.NestingLevel == 0 && Line.Level == 0) &&
+               !Left.Children.empty();
+      default:
+        break;
+      }
+    }
+
     if (Right.is(tok::r_brace) && Left.is(tok::l_brace) &&
         !Left.Children.empty())
       // Support AllowShortFunctionsOnASingleLine for JavaScript.

diff --git a/clang/unittests/Format/FormatTestJS.cpp b/clang/unittests/Format/FormatTestJS.cpp
index ef3c636..3c104b7 100644 (file)
--- a/clang/unittests/Format/FormatTestJS.cpp
+++ b/clang/unittests/Format/FormatTestJS.cpp
@@ -459,8 +459,9 @@ TEST_F(FormatTestJS, ContainerLiterals) {
   // Arrow functions in object literals.
   verifyFormat("var x = {\n"
                "  y: (a) => {\n"
+               "    x();\n"
                "    return a;\n"
-               "  }\n"
+               "  },\n"
                "};");
   verifyFormat("var x = {y: (a) => a};");
 
@@ -486,7 +487,8 @@ TEST_F(FormatTestJS, ContainerLiterals) {
 
   // Object literals can leave out labels.
   verifyFormat("f({a}, () => {\n"
-               "  g();  //\n"
+               "  x;\n"
+               "  g();\n"
                "});");
 
   // Keys can be quoted.
@@ -1112,8 +1114,9 @@ TEST_F(FormatTestJS, MultipleFunctionLiterals) {
 
 TEST_F(FormatTestJS, ArrowFunctions) {
   verifyFormat("var x = (a) => {\n"
+               "  x;\n"
                "  return a;\n"
-               "};");
+               "};\n");
   verifyFormat("var x = (a) => {\n"
                "  function y() {\n"
                "    return 42;\n"
@@ -1121,6 +1124,7 @@ TEST_F(FormatTestJS, ArrowFunctions) {
                "  return a;\n"
                "};");
   verifyFormat("var x = (a: type): {some: type} => {\n"
+               "  y;\n"
                "  return a;\n"
                "};");
   verifyFormat("var x = (a) => a;");
@@ -1147,10 +1151,41 @@ TEST_F(FormatTestJS, ArrowFunctions) {
                "        // break\n"
                "    );");
   verifyFormat("const f = (x: string|null): string|null => {\n"
+               "  y;\n"
                "  return x;\n"
                "}\n");
 }
 
+TEST_F(FormatTestJS, ArrowFunctionStyle) {
+  FormatStyle Style = getGoogleStyle(FormatStyle::LK_JavaScript);
+  Style.AllowShortLambdasOnASingleLine = FormatStyle::SLS_All;
+  verifyFormat("const arr = () => { x; };", Style);
+  verifyFormat("const arrInlineAll = () => {};", Style);
+  Style.AllowShortLambdasOnASingleLine = FormatStyle::SLS_None;
+  verifyFormat("const arr = () => {\n"
+               "  x;\n"
+               "};",
+               Style);
+  verifyFormat("const arrInlineNone = () => {\n"
+               "};",
+               Style);
+  Style.AllowShortLambdasOnASingleLine = FormatStyle::SLS_Empty;
+  verifyFormat("const arr = () => {\n"
+               "  x;\n"
+               "};",
+               Style);
+  verifyFormat("const arrInlineEmpty = () => {};",
+               Style);
+  Style.AllowShortLambdasOnASingleLine = FormatStyle::SLS_Inline;
+  verifyFormat("const arr = () => {\n"
+               "  x;\n"
+               "};",
+               Style);
+  verifyFormat("foo(() => {});",
+               Style);
+  verifyFormat("const arrInlineInline = () => {};", Style);
+}
+
 TEST_F(FormatTestJS, ReturnStatements) {
   verifyFormat("function() {\n"
                "  return [hello, world];\n"
@@ -1711,10 +1746,12 @@ TEST_F(FormatTestJS, TypeInterfaceLineWrapping) {
 TEST_F(FormatTestJS, RemoveEmptyLinesInArrowFunctions) {
   verifyFormat("x = () => {\n"
                "  foo();\n"
+               "  bar();\n"
                "};\n",
                "x = () => {\n"
                "\n"
                "  foo();\n"
+               "  bar();\n"
                "\n"
                "};\n");
 }
@@ -1791,6 +1828,10 @@ TEST_F(FormatTestJS, Modules) {
                "];");
   verifyFormat("export default [];");
   verifyFormat("export default () => {};");
+  verifyFormat("export default () => {\n"
+               "  x;\n"
+               "  x;\n"
+               "};");
   verifyFormat("export interface Foo {\n"
                "  foo: number;\n"
                "}\n"