clang-format: [JS] ASI after imports

[mprobst]

Summary

Automatic semicolon insertion should break import and export statements:

Before, this would format on one line:

// Note: no semi after 'x' below!
import {x} from 'x'
export function foo() {}

Into:

import {x} from 'x' export function foo() {}

With this change, the statements get separated.

This also improves automatic semicolon insertion to consider closing
braces preceding declarations and statements.

[klimek]

LG

lib/Format/UnwrappedLineParser.cpp

void UnwrappedLineParser::readTokenWithJavaScriptASI() {
   if (PreviousMustBeValue && Line && Line->Tokens.size() > 1) {
     // If the token before the previous one is an '@', the previous token is an
     // annotation and can precede another identifier/value.
     const FormatToken *PrePrevious = std::prev(Line->Tokens.end(), 2)->Tok;
     if (PrePrevious->is(tok::at))
       return;
   }
   if (Next->is(tok::exclaim) && PreviousMustBeValue)
-    addUnwrappedLine();
+    return addUnwrappedLine();
   bool NextMustBeValue = mustBeJSIdentOrValue(Keywords, Next);
   bool NextEndsTemplateExpr =
       Next->is(TT_TemplateString) && Next->TokenText.startswith("}");
   if (NextMustBeValue && !NextEndsTemplateExpr && !PreviousStartsTemplateExpr &&
       (PreviousMustBeValue ||
        Previous->isOneOf(tok::r_square, tok::r_paren, tok::plusplus,
                          tok::minusminus)))
-    addUnwrappedLine();
-  if (PreviousMustBeValue && isJSDeclOrStmt(Keywords, Next))
-    addUnwrappedLine();
+    return addUnwrappedLine();
+  if ((PreviousMustBeValue || Previous->is(tok::r_brace)) &&
+      isJSDeclOrStmt(Keywords, Next))
+    return addUnwrappedLine();
 }
 
 void UnwrappedLineParser::parseStructuralElement() {
   assert(!FormatTok->is(tok::l_brace));
   if (Style.Language == FormatStyle::LK_TableGen &&
       FormatTok->is(tok::pp_include)) {
     nextToken();
     if (FormatTok->is(tok::string_literal))
void UnwrappedLineParser::parseJavaScriptEs6ImportExport() {
   // For imports, `export *`, `export {...}`, consume the rest of the line up
   // to the terminating `;`. For everything else, just return and continue
   // parsing the structural element, i.e. the declaration or expression for
   // `export default`.
   if (!IsImport && !FormatTok->isOneOf(tok::l_brace, tok::star) &&
       !FormatTok->isStringLiteral())
     return;
 
-  while (!eof() && FormatTok->isNot(tok::semi)) {
+  while (!eof()) {
+    if (FormatTok->is(tok::semi))
+      return;
+    if (Line->Tokens.size() == 0) {
+      // Common issue: Automatic Semicolon Insertion wrapped the line, so the
+      // import statement should terminate.
+      return;
+    }
     if (FormatTok->is(tok::l_brace)) {
       FormatTok->BlockKind = BK_Block;
       parseBracedList();
     } else {
       nextToken();
     }
   }
 }

unittests/Format/FormatTestJS.cpp

TEST_F(FormatTestJS, AutomaticSemicolonInsertionHeuristic) {
   verifyFormat("a = 's'\n"
                "return 1",
                "a = 's'\n"
                "  return   1");
   verifyFormat("a = null\n"
                "return 1",
                "a = null\n"
                "  return   1");
+  verifyFormat(
+      "x = {a: 1}\n"
+      "class Y {}",
+      "  x  =  {a  : 1}\n"
+      "   class  Y {  }");
+}
+
+TEST_F(FormatTestJS, ImportExportASI) {
+  verifyFormat(
+      "import {x} from 'y'\n"
+      "export function z() {}",
+      "import   {x} from 'y'\n"
+      "  export function z() {}");
+  verifyFormat(
+      "export {x}\n"
+      "class Y {}",
+      "  export {x}\n"
+      "  class  Y {\n}");
 }
 
 TEST_F(FormatTestJS, ClosureStyleCasts) {
   verifyFormat("var x = /** @type {foo} */ (bar);");
 }
 
 TEST_F(FormatTestJS, TryCatch) {
   verifyFormat("try {\n"