proposal-pipe: Add support for ^^ and @@ topics

eslint/babel-eslint-parser/src/convert/convertTokens.cjs

@@ -140,6 +140,8 @@ function convertToken(token, source, tl) {
     label === tl.bracketHashL ||
     label === tl.bracketBarL ||
     label === tl.bracketBarR ||
+    label === tl.doubleCaret ||
+    label === tl.doubleAt ||
     type.isAssign
   ) {
     token.type = "Punctuator";

eslint/babel-eslint-parser/test/index.js

@@ -691,6 +691,31 @@ describe("Babel and Espree", () => {
     expect(babylonAST.tokens[16]).toMatchObject(topicToken);
   });
 
+  it.each(["^", "%", "^^", "@@"])("pipeline %s topic token", tok => {
+    const code = `
+        x |> ${tok}
+        y |> ${tok}[0]
+      `;
+
+    const babylonAST = parseForESLint(code, {
+      eslintVisitorKeys: true,
+      eslintScopeManager: true,
+      babelOptions: {
+        filename: "test.js",
+        parserOpts: {
+          plugins: [
+            ["pipelineOperator", { proposal: "hack", topicToken: tok }],
+          ],
+          tokens: true,
+        },
+      },
+    }).ast;
+
+    const topicToken = { type: "Punctuator", value: tok };
+    expect(babylonAST.tokens[2]).toMatchObject(topicToken);
+    expect(babylonAST.tokens[5]).toMatchObject(topicToken);
+  });
+
   it("empty program with line comment", () => {
     parseAndAssertSame("// single comment");
   });

packages/babel-generator/src/generators/types.ts

@@ -238,7 +238,7 @@ export function DecimalLiteral(this: Printer, node: t.DecimalLiteral) {
 }
 
 // Hack pipe operator
-const validTopicTokenSet = new Set(["^", "%", "#"]);
+const validTopicTokenSet = new Set(["^^", "@@", "^", "%", "#"]);
 export function TopicReference(this: Printer) {
   const { topicToken } = this.format;
 

packages/babel-generator/src/index.ts

@@ -203,7 +203,7 @@ export interface GeneratorOptions {
    * For use with the Hack-style pipe operator.
    * Changes what token is used for pipe bodies’ topic references.
    */
-  topicToken?: "^" | "%" | "#";
+  topicToken?: "^^" | "@@" | "^" | "%" | "#";
 }
 
 export interface GeneratorResult {

packages/babel-generator/test/fixtures/types/TopicReference-with-double-at-topicToken/input.js

@@ -0,0 +1 @@
+2 + 3 |> @@.toString(16);

packages/babel-generator/test/fixtures/types/TopicReference-with-double-at-topicToken/options.json

@@ -0,0 +1,4 @@
+{
+  "plugins": [["pipelineOperator", { "proposal": "hack", "topicToken": "@@" }]],
+  "topicToken": "@@"
+}

packages/babel-generator/test/fixtures/types/TopicReference-with-double-at-topicToken/output.js

@@ -0,0 +1 @@
+2 + 3 |> @@.toString(16);

packages/babel-generator/test/fixtures/types/TopicReference-with-double-caret-topicToken/input.js

@@ -0,0 +1 @@
+2 + 3 |> ^^.toString(16);

packages/babel-generator/test/fixtures/types/TopicReference-with-double-caret-topicToken/options.json

@@ -0,0 +1,4 @@
+{
+  "plugins": [["pipelineOperator", { "proposal": "hack", "topicToken": "^^" }]],
+  "topicToken": "^^"
+}

packages/babel-generator/test/fixtures/types/TopicReference-with-double-caret-topicToken/output.js

@@ -0,0 +1 @@
+2 + 3 |> ^^.toString(16);

packages/babel-generator/test/fixtures/types/TopicReference-with-invalid-topicToken/options.json

@@ -1,5 +1,5 @@
 {
   "plugins": [["pipelineOperator", { "proposal": "hack", "topicToken": "#" }]],
   "topicToken": "invalid",
-  "throws": "The \"topicToken\" generator option must be one of \"^\", \"%\", \"#\" (\"invalid\" received instead)."
+  "throws": "The \"topicToken\" generator option must be one of \"^^\", \"@@\", \"^\", \"%\", \"#\" (\"invalid\" received instead)."
 }

packages/babel-generator/test/fixtures/types/TopicReference-with-missing-topicToken/options.json

@@ -1,4 +1,4 @@
 {
   "plugins": [["pipelineOperator", { "proposal": "hack", "topicToken": "#" }]],
-  "throws": "The \"topicToken\" generator option must be one of \"^\", \"%\", \"#\" (undefined received instead)."
+  "throws": "The \"topicToken\" generator option must be one of \"^^\", \"@@\", \"^\", \"%\", \"#\" (undefined received instead)."
 }

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

@@ -1204,6 +1204,30 @@ export default class ExpressionParser extends LValParser {
         return this.parseTopicReferenceThenEqualsSign(tt.bitwiseXOR, "^");
       }
 
+      case tt.doubleCaret: {
+        const pipeProposal = this.getPluginOption(
+          "pipelineOperator",
+          "proposal",
+        );
+        const pluginTopicToken = this.getPluginOption(
+          "pipelineOperator",
+          "topicToken",
+        );
+
+        // The `^^` token is valid only when:
+        // the pipe-operator proposal is active,
+        // its "pipeProposal" is configured as "hack",
+        // and "topicToken" is configured as "^^".
+        // If the pipe-operator proposal settles on a token that is not ^^,
+        // then this token type may be removed.
+        if (pipeProposal === "hack" && pluginTopicToken === "^^") {
+          return this.parseTopicReference(pipeProposal);
+        } else {
+          throw this.unexpected();
+        }
+      }
+
+      case tt.doubleAt:
       case tt.bitwiseXOR:
       case tt.modulo:
       case tt.hash: {
@@ -1306,10 +1330,10 @@ export default class ExpressionParser extends LValParser {
   // that is followed by an equals sign.
   // See <https://github.com/js-choi/proposal-hack-pipes>.
   // If we find ^= or %= in an expression position
-  // (i.e., the tt.moduloAssign or tt.xorAssign token types),
-  // and if the Hack-pipes proposal is active with ^ or % as its topicToken,
-  // then the ^ or % could be the topic token (e.g., in x |> ^==y or x |> ^===y),
-  // and so we reparse the current token as ^ or %.
+  // (i.e., the tt.moduloAssign or tt.xorAssign token types), and if the
+  // Hack-pipes proposal is active with ^ or % as its topicToken, then the ^ or
+  // % could be the topic token (e.g., in x |> ^==y or x |> ^===y), and so we
+  // reparse the current token as ^ or %.
   // Otherwise, this throws an unexpected-token error.
   parseTopicReferenceThenEqualsSign(
     topicTokenType: TokenType,
@@ -1324,8 +1348,8 @@ export default class ExpressionParser extends LValParser {
       // will consume that “topic token”.
       this.state.type = topicTokenType;
       this.state.value = topicTokenValue;
-      // Rewind the tokenizer to the end of the “topic token”,
-      // so that the following token starts at the equals sign after that topic token.
+      // Rewind the tokenizer to the end of the “topic token”, so that the
+      // following token starts at the equals sign after that topic token.
       this.state.pos--;
       this.state.end--;
       // This is safe to do since the preceding character was either ^ or %, and

packages/babel-parser/src/plugin-utils.js

@@ -67,7 +67,7 @@ export function getPluginOption(
 }
 
 const PIPELINE_PROPOSALS = ["minimal", "fsharp", "hack", "smart"];
-const TOPIC_TOKENS = ["^", "%", "#"];
+const TOPIC_TOKENS = ["^^", "@@", "^", "%", "#"];
 const RECORD_AND_TUPLE_SYNTAX_TYPES = ["hash", "bar"];
 
 export function validatePlugins(plugins: PluginList) {

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

@@ -2256,7 +2256,9 @@ export default (superClass: Class<Parser>): Class<Parser> =>
         }
         // allow double nullable types in Flow: ??string
         return this.finishOp(tt.question, 1);
-      } else if (isIteratorStart(code, next)) {
+      } else if (
+        isIteratorStart(code, next, this.input.charCodeAt(this.state.pos + 2))
+      ) {
         this.state.pos += 2; // eat "@@"
         return this.readIterator();
       } else {

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

@@ -715,6 +715,10 @@ export default class Tokenizer extends ParserErrors {
 
   readToken_caret(): void {
     const next = this.input.charCodeAt(this.state.pos + 1);
+    const pipeProposal = this.getPluginOption("pipelineOperator", "proposal");
+    const topicToken = this.getPluginOption("pipelineOperator", "topicToken");
+    const hackPipeWithDoubleCaretIsActive =
+      pipeProposal === "hack" && topicToken === "^^";
 
     // '^='
     if (next === charCodes.equalsTo && !this.state.inType) {
@@ -723,12 +727,43 @@ export default class Tokenizer extends ParserErrors {
       // it can be merged with tt.assign.
       this.finishOp(tt.xorAssign, 2);
     }
+    // '^^'
+    else if (hackPipeWithDoubleCaretIsActive && next === charCodes.caret) {
+      // `tt.doubleCaret` is only needed to support ^^
+      // as a Hack-pipe topic token.
+      // If the proposal ends up choosing a different token,
+      // it may be removed.
+      this.finishOp(tt.doubleCaret, 2);
+
+      // `^^^` is forbidden and must be separated by a space.
+      const lookaheadCh = this.input.codePointAt(this.state.pos);
+      if (lookaheadCh === charCodes.caret) {
+        throw this.unexpected();
+      }
+    }
     // '^'
     else {
       this.finishOp(tt.bitwiseXOR, 1);
     }
   }
 
+  readToken_atSign(): void {
+    const next = this.input.charCodeAt(this.state.pos + 1);
+
+    // '@@'
+    if (next === charCodes.atSign) {
+      // `tt.doubleAt` is only needed to support @@
+      // as a Hack-pipe topic token.
+      // If the proposal ends up choosing a different token,
+      // it may be removed.
+      this.finishOp(tt.doubleAt, 2);
+    }
+    // '@'
+    else {
+      this.finishOp(tt.at, 1);
+    }
+  }
+
   readToken_plus_min(code: number): void {
     // '+-'
     const next = this.input.charCodeAt(this.state.pos + 1);
@@ -1018,8 +1053,7 @@ export default class Tokenizer extends ParserErrors {
         return;
 
       case charCodes.atSign:
-        ++this.state.pos;
-        this.finishToken(tt.at);
+        this.readToken_atSign();
         return;
 
       case charCodes.numberSign:

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

@@ -186,15 +186,22 @@ export const tt: { [name: string]: TokenType } = {
   eq: createToken("=", { beforeExpr, isAssign }),
   assign: createToken("_=", { beforeExpr, isAssign }),
   slashAssign: createToken("_=", { beforeExpr, isAssign }),
-  // These are only needed to support % and ^ as a Hack-pipe topic token. When the
-  // proposal settles on a token, the others can be merged with tt.assign.
+  // These are only needed to support % and ^ as a Hack-pipe topic token.
+  // When the proposal settles on a token, the others can be merged with
+  // tt.assign.
   xorAssign: createToken("_=", { beforeExpr, isAssign }),
   moduloAssign: createToken("_=", { beforeExpr, isAssign }),
   // end: isAssign
 
   incDec: createToken("++/--", { prefix, postfix, startsExpr }),
   bang: createToken("!", { beforeExpr, prefix, startsExpr }),
   tilde: createToken("~", { beforeExpr, prefix, startsExpr }),
+
+  // More possible topic tokens.
+  // When the proposal settles on a token, at least one of these may be removed.
+  doubleCaret: createToken("^^", { startsExpr }),
+  doubleAt: createToken("@@", { startsExpr }),
+
   // start: isBinop
   pipeline: createBinop("|>", 0),
   nullishCoalescing: createBinop("??", 1),

packages/babel-parser/src/util/identifier.js

@@ -3,6 +3,7 @@
 // @flow
 
 import * as charCodes from "charcodes";
+import { isIdentifierStart } from "@babel/helper-validator-identifier";
 
 export {
   isIdentifierStart,
@@ -18,8 +19,16 @@ export const keywordRelationalOperator = /^in(stanceof)?$/;
 
 // Test whether a current state character code and next character code is @
 
-export function isIteratorStart(current: number, next: number): boolean {
-  return current === charCodes.atSign && next === charCodes.atSign;
+export function isIteratorStart(
+  current: number,
+  next: number,
+  next2: number,
+): boolean {
+  return (
+    current === charCodes.atSign &&
+    next === charCodes.atSign &&
+    isIdentifierStart(next2)
+  );
 }
 
 // This is the comprehensive set of JavaScript reserved words

packages/babel-parser/test/fixtures/experimental/pipeline-operator/hack-double-at-proposal-addition-with-topic-first/input.js

@@ -0,0 +1 @@
+value |> @@ + 1

packages/babel-parser/test/fixtures/experimental/pipeline-operator/hack-double-at-proposal-addition-with-topic-first/options.json

@@ -0,0 +1,3 @@
+{
+  "plugins": [["pipelineOperator", { "proposal": "hack", "topicToken": "@@" }]]
+}

packages/babel-parser/test/fixtures/experimental/pipeline-operator/hack-double-at-proposal-addition-with-topic-first/output.json

@@ -0,0 +1,45 @@
+{
+  "type": "File",
+  "start":0,"end":15,"loc":{"start":{"line":1,"column":0},"end":{"line":1,"column":15}},
+  "program": {
+    "type": "Program",
+    "start":0,"end":15,"loc":{"start":{"line":1,"column":0},"end":{"line":1,"column":15}},
+    "sourceType": "script",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "ExpressionStatement",
+        "start":0,"end":15,"loc":{"start":{"line":1,"column":0},"end":{"line":1,"column":15}},
+        "expression": {
+          "type": "BinaryExpression",
+          "start":0,"end":15,"loc":{"start":{"line":1,"column":0},"end":{"line":1,"column":15}},
+          "left": {
+            "type": "Identifier",
+            "start":0,"end":5,"loc":{"start":{"line":1,"column":0},"end":{"line":1,"column":5},"identifierName":"value"},
+            "name": "value"
+          },
+          "operator": "|>",
+          "right": {
+            "type": "BinaryExpression",
+            "start":9,"end":15,"loc":{"start":{"line":1,"column":9},"end":{"line":1,"column":15}},
+            "left": {
+              "type": "TopicReference",
+              "start":9,"end":11,"loc":{"start":{"line":1,"column":9},"end":{"line":1,"column":11}}
+            },
+            "operator": "+",
+            "right": {
+              "type": "NumericLiteral",
+              "start":14,"end":15,"loc":{"start":{"line":1,"column":14},"end":{"line":1,"column":15}},
+              "extra": {
+                "rawValue": 1,
+                "raw": "1"
+              },
+              "value": 1
+            }
+          }
+        }
+      }
+    ],
+    "directives": []
+  }
+}

packages/babel-parser/test/fixtures/experimental/pipeline-operator/hack-double-at-proposal-addition-with-topic-last/input.js

@@ -0,0 +1 @@
+value |> 1 + @@

packages/babel-parser/test/fixtures/experimental/pipeline-operator/hack-double-at-proposal-addition-with-topic-last/options.json

@@ -0,0 +1,3 @@
+{
+  "plugins": [["pipelineOperator", { "proposal": "hack", "topicToken": "@@" }]]
+}

packages/babel-parser/test/fixtures/experimental/pipeline-operator/hack-double-at-proposal-addition-with-topic-last/output.json

@@ -0,0 +1,45 @@
+{
+  "type": "File",
+  "start":0,"end":15,"loc":{"start":{"line":1,"column":0},"end":{"line":1,"column":15}},
+  "program": {
+    "type": "Program",
+    "start":0,"end":15,"loc":{"start":{"line":1,"column":0},"end":{"line":1,"column":15}},
+    "sourceType": "script",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "ExpressionStatement",
+        "start":0,"end":15,"loc":{"start":{"line":1,"column":0},"end":{"line":1,"column":15}},
+        "expression": {
+          "type": "BinaryExpression",
+          "start":0,"end":15,"loc":{"start":{"line":1,"column":0},"end":{"line":1,"column":15}},
+          "left": {
+            "type": "Identifier",
+            "start":0,"end":5,"loc":{"start":{"line":1,"column":0},"end":{"line":1,"column":5},"identifierName":"value"},
+            "name": "value"
+          },
+          "operator": "|>",
+          "right": {
+            "type": "BinaryExpression",
+            "start":9,"end":15,"loc":{"start":{"line":1,"column":9},"end":{"line":1,"column":15}},
+            "left": {
+              "type": "NumericLiteral",
+              "start":9,"end":10,"loc":{"start":{"line":1,"column":9},"end":{"line":1,"column":10}},
+              "extra": {
+                "rawValue": 1,
+                "raw": "1"
+              },
+              "value": 1
+            },
+            "operator": "+",
+            "right": {
+              "type": "TopicReference",
+              "start":13,"end":15,"loc":{"start":{"line":1,"column":13},"end":{"line":1,"column":15}}
+            }
+          }
+        }
+      }
+    ],
+    "directives": []
+  }
+}

packages/babel-parser/test/fixtures/experimental/pipeline-operator/hack-double-at-proposal-addition-without-topic/input.js

@@ -0,0 +1 @@
+value |> a + b

packages/babel-parser/test/fixtures/experimental/pipeline-operator/hack-double-at-proposal-addition-without-topic/options.json

@@ -0,0 +1,3 @@
+{
+  "plugins": [["pipelineOperator", { "proposal": "hack", "topicToken": "@@" }]]
+}