Simplify pipeline parsing with using declarations

babel.config.js

@@ -182,6 +182,8 @@ module.exports = function (api) {
  plugins: [
  ["@babel/transform-object-rest-spread", { useBuiltIns: true }],
 
+ "@babel/plugin-proposal-explicit-resource-management",
+
  convertESM ? "@babel/transform-export-namespace-from" : null,
 
  pluginPackageJsonMacro,

eslint.config.js

@@ -97,7 +97,10 @@ module.exports = [
  rules: {
  ...config.rules,
  "no-unused-vars": "off",
- "@typescript-eslint/no-unused-vars": "error",
+ "@typescript-eslint/no-unused-vars": [
+ "error",
+ { varsIgnorePattern: "^_" },
+ ],
  "no-dupe-class-members": "off",
  "@typescript-eslint/no-dupe-class-members": "error",
  "no-undef": "off",

package.json

@@ -27,6 +27,7 @@
  "@babel/eslint-parser": "workspace:^",
  "@babel/eslint-plugin-development": "workspace:^",
  "@babel/eslint-plugin-development-internal": "workspace:^",
+ "@babel/plugin-proposal-explicit-resource-management": "8.0.0-alpha.5",
  "@babel/plugin-transform-dynamic-import": "8.0.0-alpha.5",
  "@babel/plugin-transform-export-namespace-from": "8.0.0-alpha.5",
  "@babel/plugin-transform-modules-commonjs": "8.0.0-alpha.5",

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

@@ -514,26 +514,27 @@ export default abstract class ExpressionParser extends LValParser {
  switch (op) {
  case tt.pipeline:
  switch (this.getPluginOption("pipelineOperator", "proposal")) {
- case "hack":
- return this.withTopicBindingContext(() => {
- return this.parseHackPipeBody();
- });
-
- case "smart":
- return this.withTopicBindingContext(() => {
- if (this.prodParam.hasYield && this.isContextual(tt._yield)) {
- throw this.raise(Errors.PipeBodyIsTighter, this.state.startLoc);
- }
- return this.parseSmartPipelineBodyInStyle(
- this.parseExprOpBaseRightExpr(op, prec),
- startLoc,
- );
- });
+ case "hack": {
+ using _ = this.withState("topicReferenceUsage", { used: false });
+ return this.parseHackPipeBody();
+ }
+
+ case "smart": {
+ if (this.prodParam.hasYield && this.isContextual(tt._yield)) {
+ throw this.raise(Errors.PipeBodyIsTighter, this.state.startLoc);
+ }
 
- case "fsharp":
- return this.withSoloAwaitPermittingContext(() => {
- return this.parseFSharpPipelineBody(prec);
- });
+ using _ = this.withState("topicReferenceUsage", { used: false });
+ return this.parseSmartPipelineBodyInStyle(
+ this.parseExprOpBaseRightExpr(op, prec),
+ startLoc,
+ );
+ }
+
+ case "fsharp": {
+ using _ = this.withState("soloAwait", true);
+ return this.parseFSharpPipelineBody(prec);
+ }
  }
 
  // Falls through.
@@ -573,7 +574,7 @@ export default abstract class ExpressionParser extends LValParser {
  type: body.type as UnparenthesizedPipeBodyTypes,
  });
  }
- if (!this.topicReferenceWasUsedInCurrentContext()) {
+ if (!this.state.topicReferenceUsage.used) {
  // A Hack pipe body must use the topic reference at least once.
  this.raise(Errors.PipeTopicUnused, startLoc);
  }
@@ -1001,10 +1002,10 @@ export default abstract class ExpressionParser extends LValParser {
  nodeForExtra?: N.Node | null,
  refExpressionErrors?: ExpressionErrors | null,
  ): Array<N.Expression | undefined | null> {
+ using _ = this.withState("inFSharpPipelineDirectBody", false);
+
  const elts: N.Expression[] = [];
  let first = true;
- const oldInFSharpPipelineDirectBody = this.state.inFSharpPipelineDirectBody;
- this.state.inFSharpPipelineDirectBody = false;
 
  while (!this.eat(close)) {
  if (first) {
@@ -1036,8 +1037,6 @@ export default abstract class ExpressionParser extends LValParser {
  );
  }
 
- this.state.inFSharpPipelineDirectBody = oldInFSharpPipelineDirectBody;
-
  return elts;
  }
 
@@ -1435,7 +1434,7 @@ export default abstract class ExpressionParser extends LValParser {
  // as enforced by testTopicReferenceConfiguration.
  "TopicReference";
 
- if (!this.topicReferenceIsAllowedInCurrentContext()) {
+ if (!this.state.topicReferenceUsage) {
  this.raise(
  // The topic reference is not allowed in the current context:
  // it is outside of a pipe body.
@@ -1446,12 +1445,12 @@ export default abstract class ExpressionParser extends LValParser {
  Errors.PipeTopicUnbound,
  startLoc,
  );
+ } else {
+ // Register the topic reference so that its pipe body knows
+ // that its topic was used at least once.
+ this.state.topicReferenceUsage.used = true;
  }
 
- // Register the topic reference so that its pipe body knows
- // that its topic was used at least once.
- this.registerTopicReference();
-
  return this.finishNode(node, nodeType);
  } else {
  // The token does not match the plugin’s configuration.
@@ -1752,60 +1751,57 @@ export default abstract class ExpressionParser extends LValParser {
  this.next(); // eat `(`
  this.expressionScope.enter(newArrowHeadScope());
 
- const oldMaybeInArrowParameters = this.state.maybeInArrowParameters;
- const oldInFSharpPipelineDirectBody = this.state.inFSharpPipelineDirectBody;
- this.state.maybeInArrowParameters = true;
- this.state.inFSharpPipelineDirectBody = false;
-
  const innerStartLoc = this.state.startLoc;
  const exprList: N.Expression[] = [];
  const refExpressionErrors = new ExpressionErrors();
  let first = true;
  let spreadStartLoc;
  let optionalCommaStartLoc;
 
- while (!this.match(tt.parenR)) {
- if (first) {
- first = false;
- } else {
- this.expect(
- tt.comma,
- refExpressionErrors.optionalParametersLoc === null
- ? null
- : refExpressionErrors.optionalParametersLoc,
- );
- if (this.match(tt.parenR)) {
- optionalCommaStartLoc = this.state.startLoc;
- break;
+ {
+ using _1 = this.withState("maybeInArrowParameters", true);
+ using _2 = this.withState("inFSharpPipelineDirectBody", false);
+
+ while (!this.match(tt.parenR)) {
+ if (first) {
+ first = false;
+ } else {
+ this.expect(
+ tt.comma,
+ refExpressionErrors.optionalParametersLoc === null
+ ? null
+ : refExpressionErrors.optionalParametersLoc,
+ );
+ if (this.match(tt.parenR)) {
+ optionalCommaStartLoc = this.state.startLoc;
+ break;
+ }
  }
- }
 
- if (this.match(tt.ellipsis)) {
- const spreadNodeStartLoc = this.state.startLoc;
- spreadStartLoc = this.state.startLoc;
- exprList.push(
- this.parseParenItem(this.parseRestBinding(), spreadNodeStartLoc),
- );
+  if (this.match(tt.ellipsis)) {
+  const spreadNodeStartLoc = this.state.startLoc;
+  spreadStartLoc = this.state.startLoc;
+  exprList.push(
+  this.parseParenItem(this.parseRestBinding(), spreadNodeStartLoc),
+  );
 
- if (!this.checkCommaAfterRest(charCodes.rightParenthesis)) {
- break;
+ if (!this.checkCommaAfterRest(charCodes.rightParenthesis)) {
+ break;
+ }
+ } else {
+ exprList.push(
+ this.parseMaybeAssignAllowIn(
+ refExpressionErrors,
+ this.parseParenItem,
+ ),
+ );
  }
- } else {
- exprList.push(
- this.parseMaybeAssignAllowIn(
- refExpressionErrors,
- this.parseParenItem,
- ),
- );
  }
  }
 
  const innerEndLoc = this.state.lastTokEndLoc;
  this.expect(tt.parenR);
 
- this.state.maybeInArrowParameters = oldMaybeInArrowParameters;
- this.state.inFSharpPipelineDirectBody = oldInFSharpPipelineDirectBody;
-
  let arrowNode = this.startNodeAt<N.ArrowFunctionExpression>(startLoc);
  if (
  canBeArrow &&
@@ -2037,8 +2033,8 @@ export default abstract class ExpressionParser extends LValParser {
  if (isRecord) {
  this.expectPlugin("recordAndTuple");
  }
- const oldInFSharpPipelineDirectBody = this.state.inFSharpPipelineDirectBody;
- this.state.inFSharpPipelineDirectBody = false;
+ using _ = this.withState("inFSharpPipelineDirectBody", false);
+
  const propHash: any = Object.create(null);
  let first = true;
  const node = this.startNode<
@@ -2089,7 +2085,6 @@ export default abstract class ExpressionParser extends LValParser {
 
  this.next();
 
- this.state.inFSharpPipelineDirectBody = oldInFSharpPipelineDirectBody;
  let type = "ObjectExpression";
  if (isPattern) {
  type = "ObjectPattern";
@@ -2467,8 +2462,8 @@ export default abstract class ExpressionParser extends LValParser {
  if (isTuple) {
  this.expectPlugin("recordAndTuple");
  }
- const oldInFSharpPipelineDirectBody = this.state.inFSharpPipelineDirectBody;
- this.state.inFSharpPipelineDirectBody = false;
+ using _ = this.withState("inFSharpPipelineDirectBody", false);
+
  const node = this.startNode<N.ArrayExpression | N.TupleExpression>();
  this.next();
  node.elements = this.parseExprList(
@@ -2478,7 +2473,6 @@ export default abstract class ExpressionParser extends LValParser {
  // @ts-expect-error todo(flow->ts)
  node,
  );
- this.state.inFSharpPipelineDirectBody = oldInFSharpPipelineDirectBody;
  return this.finishNode(
  node,
  isTuple ? "TupleExpression" : "ArrayExpression",
@@ -3027,74 +3021,19 @@ export default abstract class ExpressionParser extends LValParser {
  }
 
  // A topic-style smart-mix pipe body must use the topic reference at least once.
- if (!this.topicReferenceWasUsedInCurrentContext()) {
+ if (!this.state.topicReferenceUsage.used) {
  this.raise(Errors.PipelineTopicUnused, startLoc);
  }
  }
 
- // Enable topic references from outer contexts within Hack-style pipe bodies.
- // The function modifies the parser's topic-context state to enable or disable
- // the use of topic references.
- // The function then calls a callback, then resets the parser
- // to the old topic-context state that it had before the function was called.
-
- withTopicBindingContext<T>(callback: () => T): T {
- const outerContextTopicState = this.state.topicContext;
- this.state.topicContext = {
- // Enable the use of the primary topic reference.
- maxNumOfResolvableTopics: 1,
- // Hide the use of any topic references from outer contexts.
- maxTopicIndex: null,
- };
-
- try {
- return callback();
- } finally {
- this.state.topicContext = outerContextTopicState;
- }
- }
-
  // This helper method is used only with the deprecated smart-mix pipe proposal.
  // Disables topic references from outer contexts within syntax constructs
  // such as the bodies of iteration statements.
- // The function modifies the parser's topic-context state to enable or disable
- // the use of topic references with the smartPipelines plugin. They then run a
- // callback, then they reset the parser to the old topic-context state that it
- // had before the function was called.
 
- withSmartMixTopicForbiddingContext<T>(callback: () => T): T {
+ withSmartMixTopicForbiddingContext(): Disposable | undefined {
  if (this.hasPlugin(["pipelineOperator", { proposal: "smart" }])) {
  // Reset the parser’s topic context only if the smart-mix pipe proposal is active.
- const outerContextTopicState = this.state.topicContext;
- this.state.topicContext = {
- // Disable the use of the primary topic reference.
- maxNumOfResolvableTopics: 0,
- // Hide the use of any topic references from outer contexts.
- maxTopicIndex: null,
- };
-
- try {
- return callback();
- } finally {
- this.state.topicContext = outerContextTopicState;
- }
- } else {
- // If the pipe proposal is "minimal", "fsharp", or "hack",
- // or if no pipe proposal is active,
- // then the callback result is returned
- // without touching any extra parser state.
- return callback();
- }
- }
-
- withSoloAwaitPermittingContext<T>(callback: () => T): T {
- const outerContextSoloAwaitState = this.state.soloAwait;
- this.state.soloAwait = true;
-
- try {
- return callback();
- } finally {
- this.state.soloAwait = outerContextSoloAwaitState;
+ return this.withState("topicReferenceUsage", null);
  }
  }
 
@@ -3126,38 +3065,18 @@ export default abstract class ExpressionParser extends LValParser {
  return callback();
  }
 
- // Register the use of a topic reference within the current
- // topic-binding context.
- registerTopicReference(): void {
- this.state.topicContext.maxTopicIndex = 0;
- }
-
- topicReferenceIsAllowedInCurrentContext(): boolean {
- return this.state.topicContext.maxNumOfResolvableTopics >= 1;
- }
-
- topicReferenceWasUsedInCurrentContext(): boolean {
- return (
- this.state.topicContext.maxTopicIndex != null &&
- this.state.topicContext.maxTopicIndex >= 0
- );
- }
-
  parseFSharpPipelineBody(this: Parser, prec: number): N.Expression {
  const startLoc = this.state.startLoc;
 
  this.state.potentialArrowAt = this.state.start;
- const oldInFSharpPipelineDirectBody = this.state.inFSharpPipelineDirectBody;
- this.state.inFSharpPipelineDirectBody = true;
+ using _ = this.withState("inFSharpPipelineDirectBody", true);
 
  const ret = this.parseExprOp(
  this.parseMaybeUnaryOrPrivate(),
  startLoc,
  prec,
  );
 
- this.state.inFSharpPipelineDirectBody = oldInFSharpPipelineDirectBody;
-
  return ret;
  }