Simplifiy tracking of valid JSX positions (#13891)

Remove `state.inPropertyName` and simplifies `state.canStartJSXElement` tracking

packages/babel-parser/src/parser/expression.js

@@ -22,12 +22,12 @@ import {
   tokenCanStartExpression,
   tokenIsAssignment,
   tokenIsIdentifier,
-  tokenIsKeyword,
   tokenIsKeywordOrIdentifier,
   tokenIsOperator,
   tokenIsPostfix,
   tokenIsPrefix,
   tokenIsRightAssociative,
+  tokenKeywordOrIdentifierIsKeyword,
   tokenLabelName,
   tokenOperatorPrecedence,
   tt,
@@ -2237,8 +2237,6 @@ export default class ExpressionParser extends LValParser {
       prop.key = this.parseMaybeAssignAllowIn();
       this.expect(tt.bracketR);
     } else {
-      const oldInPropertyName = this.state.inPropertyName;
-      this.state.inPropertyName = true;
       // We check if it's valid for it to be a private name when we push it.
       const type = this.state.type;
       (prop: $FlowFixMe).key =
@@ -2253,8 +2251,6 @@ export default class ExpressionParser extends LValParser {
         // ClassPrivateProperty is never computed, so we don't assign in that case.
         prop.computed = false;
       }
-
-      this.state.inPropertyName = oldInPropertyName;
     }
 
     return prop.key;
@@ -2584,12 +2580,16 @@ export default class ExpressionParser extends LValParser {
       throw this.unexpected();
     }
 
+    const tokenIsKeyword = tokenKeywordOrIdentifierIsKeyword(type);
+
     if (liberal) {
       // If the current token is not used as a keyword, set its type to "tt.name".
       // This will prevent this.next() from throwing about unexpected escapes.
-      this.state.type = tt.name;
+      if (tokenIsKeyword) {
+        this.replaceToken(tt.name);
+      }
     } else {
-      this.checkReservedWord(name, start, tokenIsKeyword(type), false);
+      this.checkReservedWord(name, start, tokenIsKeyword, false);
     }
 
     this.next();

packages/babel-parser/src/plugins/jsx/index.js

@@ -21,10 +21,6 @@ import { isIdentifierChar, isIdentifierStart } from "../../util/identifier";
 import type { Position } from "../../util/location";
 import { isNewLine } from "../../util/whitespace";
 import { Errors, makeErrorTemplates, ErrorCodes } from "../../parser/error";
-import type { LookaheadState } from "../../tokenizer/state";
-import State from "../../tokenizer/state";
-
-type JSXLookaheadState = LookaheadState & { inPropertyName: boolean };
 
 const HEX_NUMBER = /^[\da-fA-F]+$/;
 const DECIMAL_NUMBER = /^\d+$/;
@@ -106,7 +102,7 @@ export default (superClass: Class<Parser>): Class<Parser> =>
           case charCodes.lessThan:
           case charCodes.leftCurlyBrace:
             if (this.state.pos === this.state.start) {
-              if (ch === charCodes.lessThan && this.state.exprAllowed) {
+              if (ch === charCodes.lessThan && this.state.canStartJSXElement) {
                 ++this.state.pos;
                 return this.finishToken(tt.jsxTagStart);
               }
@@ -556,24 +552,14 @@ export default (superClass: Class<Parser>): Class<Parser> =>
       ) {
         // In case we encounter an lt token here it will always be the start of
         // jsx as the lt sign is not allowed in places that expect an expression
-        this.finishToken(tt.jsxTagStart);
+        this.replaceToken(tt.jsxTagStart);
         return this.jsxParseElement();
       } else {
         return super.parseExprAtom(refExpressionErrors);
       }
     }
 
-    createLookaheadState(state: State): JSXLookaheadState {
-      const lookaheadState = ((super.createLookaheadState(
-        state,
-      ): any): JSXLookaheadState);
-      lookaheadState.inPropertyName = state.inPropertyName;
-      return lookaheadState;
-    }
-
     getTokenFromCode(code: number): void {
-      if (this.state.inPropertyName) return super.getTokenFromCode(code);
-
       const context = this.curContext();
 
       if (context === tc.j_expr) {
@@ -600,7 +586,7 @@ export default (superClass: Class<Parser>): Class<Parser> =>
 
       if (
         code === charCodes.lessThan &&
-        this.state.exprAllowed &&
+        this.state.canStartJSXElement &&
         this.input.charCodeAt(this.state.pos + 1) !== charCodes.exclamationMark
       ) {
         ++this.state.pos;
@@ -617,7 +603,7 @@ export default (superClass: Class<Parser>): Class<Parser> =>
         // do not consider JSX expr -> JSX open tag -> ... anymore
         // reconsider as closing tag context
         context.splice(-2, 2, tc.j_cTag);
-        this.state.exprAllowed = false;
+        this.state.canStartJSXElement = false;
       } else if (type === tt.jsxTagStart) {
         context.push(
           tc.j_expr, // treat as beginning of JSX expression
@@ -627,17 +613,13 @@ export default (superClass: Class<Parser>): Class<Parser> =>
         const out = context.pop();
         if ((out === tc.j_oTag && prevType === tt.slash) || out === tc.j_cTag) {
           context.pop();
-          this.state.exprAllowed = context[context.length - 1] === tc.j_expr;
+          this.state.canStartJSXElement =
+            context[context.length - 1] === tc.j_expr;
         } else {
-          this.state.exprAllowed = true;
+          this.state.canStartJSXElement = true;
         }
-      } else if (
-        tokenIsKeyword(type) &&
-        (prevType === tt.dot || prevType === tt.questionDot)
-      ) {
-        this.state.exprAllowed = false;
       } else {
-        this.state.exprAllowed = tokenComesBeforeExpression(type);
+        this.state.canStartJSXElement = tokenComesBeforeExpression(type);
       }
     }
   };

packages/babel-parser/src/plugins/typescript/index.js

@@ -2125,7 +2125,7 @@ export default (superClass: Class<Parser>): Class<Parser> =>
         // When ! is consumed as a postfix operator (non-null assertion),
         // disallow JSX tag forming after. e.g. When parsing `p! < n.p!`
         // `<n.p` can not be a start of JSX tag
-        this.state.exprAllowed = false;
+        this.state.canStartJSXElement = false;
         this.next();
 
         const nonNullExpression: N.TsNonNullExpression = this.startNodeAt(

packages/babel-parser/src/tokenizer/index.js

@@ -482,7 +482,7 @@ export default class Tokenizer extends ParserErrors {
   }
 
   // Called at the end of every token. Sets `end`, `val`, and
-  // maintains `context` and `exprAllowed`, and skips the space after
+  // maintains `context` and `canStartJSXElement`, and skips the space after
   // the token, so that the next one's `start` will point at the
   // right position.
 
@@ -498,6 +498,14 @@ export default class Tokenizer extends ParserErrors {
     }
   }
 
+  replaceToken(type: TokenType): void {
+    this.state.type = type;
+    // the prevType of updateContext is required
+    // only when the new type is tt.slash/tt.jsxTagEnd
+    // $FlowIgnore
+    this.updateContext();
+  }
+
   // ### Token reading
 
   // This is the function that is called to fetch the next token. It

packages/babel-parser/src/tokenizer/state.js

@@ -68,7 +68,6 @@ export default class State {
   maybeInArrowParameters: boolean = false;
   inType: boolean = false;
   noAnonFunctionType: boolean = false;
-  inPropertyName: boolean = false;
   hasFlowComment: boolean = false;
   isAmbientContext: boolean = false;
   inAbstractClass: boolean = false;
@@ -127,7 +126,7 @@ export default class State {
   // or ends a string template
   context: Array<TokContext> = [ct.brace];
   // Used to track whether a JSX element is allowed to form
-  exprAllowed: boolean = true;
+  canStartJSXElement: boolean = true;
 
   // Used to signal to callers of `readWord1` whether the word
   // contained any escape sequences. This is needed because words with

packages/babel-parser/src/tokenizer/types.js

@@ -332,6 +332,12 @@ export function tokenIsIdentifier(token: TokenType): boolean {
   return token >= tt._as && token <= tt.name;
 }
 
+export function tokenKeywordOrIdentifierIsKeyword(token: TokenType): boolean {
+  // we can remove the token >= tt._in check when we
+  // know a token is either keyword or identifier
+  return token <= tt._while;
+}
+
 export function tokenIsKeywordOrIdentifier(token: TokenType): boolean {
   return token >= tt._in && token <= tt.name;
 }