clang-format: [JS] pragmas for tslint, tsc.

[mprobst]

Summary

tslint and tsc (the TypeScript compiler itself) use comment pragmas of
the style:

// tslint:disable-next-line:foo
// @ts-ignore

These must not be wrapped and must stay on their own line, in isolation.
For tslint, this required adding it to the pragma regexp. The comments
starting with @ are already left alone, but this change adds test
coverage for them.

clang/lib/Format/Format.cpp

if (Language == FormatStyle::LK_Java) {
     GoogleStyle.SpaceAfterCStyleCast = true;
     GoogleStyle.SpacesBeforeTrailingComments = 1;
   } else if (Language == FormatStyle::LK_JavaScript) {
     GoogleStyle.AlignAfterOpenBracket = FormatStyle::BAS_AlwaysBreak;
     GoogleStyle.AlignOperands = false;
     GoogleStyle.AllowShortFunctionsOnASingleLine = FormatStyle::SFS_Empty;
     GoogleStyle.AlwaysBreakBeforeMultilineStrings = false;
     GoogleStyle.BreakBeforeTernaryOperators = false;
-    // taze:, triple slash directives (`/// <...`), @see, which is commonly
-    // followed by overlong URLs.
-    GoogleStyle.CommentPragmas = "(taze:|^/[ \t]*<|@see)";
+    // taze:, triple slash directives (`/// <...`), tslint:, and @see, which is
+    // commonly followed by overlong URLs.
+    GoogleStyle.CommentPragmas = "(taze:|^/[ \t]*<|tslint:|@see)";
     GoogleStyle.MaxEmptyLinesToKeep = 3;
     GoogleStyle.NamespaceIndentation = FormatStyle::NI_All;
     GoogleStyle.SpacesInContainerLiterals = false;
     GoogleStyle.JavaScriptQuotes = FormatStyle::JSQS_Single;
     GoogleStyle.JavaScriptWrapImports = false;
   } else if (Language == FormatStyle::LK_Proto) {
     GoogleStyle.AllowShortFunctionsOnASingleLine = FormatStyle::SFS_Empty;
     GoogleStyle.AlwaysBreakBeforeMultilineStrings = false;

clang/unittests/Format/FormatTestJS.cpp

EXPECT_EQ("{\n"
                    " * long long long long\n"
                    " * long\n"
                    " */\n"
                    "  function f(a) {}\n"
                    "}",
                    getGoogleJSStyleWithColumns(20)));
 }
 
+TEST_F(FormatTestJS, TslintComments) {
+  // tslint uses pragma comments that must be on their own line.
+  verifyFormat("// Comment that needs wrapping. Comment that needs wrapping. "
+               "Comment that needs\n"
+               "// wrapping. Trailing line.\n"
+               "// tslint:disable-next-line:must-be-on-own-line",
+               "// Comment that needs wrapping. Comment that needs wrapping. "
+               "Comment that needs wrapping.\n"
+               "// Trailing line.\n"
+               "// tslint:disable-next-line:must-be-on-own-line");
+}
+
+TEST_F(FormatTestJS, TscComments) {
+  // As above, @ts-ignore and @ts-check comments must be on their own line.
+  verifyFormat("// Comment that needs wrapping. Comment that needs wrapping. "
+               "Comment that needs\n"
+               "// wrapping. Trailing line.\n"
+               "// @ts-ignore",
+               "// Comment that needs wrapping. Comment that needs wrapping. "
+               "Comment that needs wrapping.\n"
+               "// Trailing line.\n"
+               "// @ts-ignore");
+  verifyFormat("// Comment that needs wrapping. Comment that needs wrapping. "
+               "Comment that needs\n"
+               "// wrapping. Trailing line.\n"
+               "// @ts-check",
+               "// Comment that needs wrapping. Comment that needs wrapping. "
+               "Comment that needs wrapping.\n"
+               "// Trailing line.\n"
+               "// @ts-check");
+}
+
 TEST_F(FormatTestJS, RequoteStringsSingle) {
   verifyFormat("var x = 'foo';", "var x = \"foo\";");
   verifyFormat("var x = 'fo\\'o\\'';", "var x = \"fo'o'\";");
   verifyFormat("var x = 'fo\\'o\\'';", "var x = \"fo\\'o'\";");
   verifyFormat(
       "var x =\n"
       "    'foo\\'';",
       // Code below is 15 chars wide, doesn't fit into the line with the