Pipeline Operator proposal

README.md

@@ -149,6 +149,7 @@ require("babylon").parse("code", {
 | `bigInt` ([proposal](https://github.com/tc39/proposal-bigint)) | `100n` |
 | `optionalCatchBinding` ([proposal](https://github.com/babel/proposals/issues/7)) | `try {throw 0;} catch{do();}` |
 | `throwExpressions` ([proposal](https://github.com/babel/proposals/issues/23)) | `() => throw new Error("")` |
+| `pipelineOperator` ([proposal](https://github.com/babel/proposals/issues/29)) | `a |> b` |
 
 ### FAQ
 

ast/spec.md

@@ -790,6 +790,7 @@ enum BinaryOperator {
      | "+" | "-" | "*" | "/" | "%"
      | "|" | "^" | "&" | "in"
      | "instanceof"
+     | "|>"
 }
 ```
 

src/parser/expression.js

@@ -290,6 +290,13 @@ export default class ExpressionParser extends LValParser {
 
         const startPos = this.state.start;
         const startLoc = this.state.startLoc;
+
+        if (node.operator === "|>") {
+          this.expectPlugin("pipelineOperator");
+          // Support syntax such as 10 |> x => x + 1
+          this.state.potentialArrowAt = startPos;
+        }
+
         node.right = this.parseExprOp(
           this.parseMaybeUnary(),
           startPos,

src/tokenizer/index.js

@@ -411,9 +411,16 @@ export default class Tokenizer extends LocationParser {
     const next = this.input.charCodeAt(this.state.pos + 1);
     if (next === code)
       return this.finishOp(code === 124 ? tt.logicalOR : tt.logicalAND, 2);
+    if (code === 124) {
+      // '|>'
+      if (next === 62) {
+        return this.finishOp(tt.pipeline, 2);
+      } else if (next === 125 && this.hasPlugin("flow")) {
+        // '|}'
+        return this.finishOp(tt.braceBarR, 2);
+      }
+    }
     if (next === 61) return this.finishOp(tt.assign, 2);
-    if (code === 124 && next === 125 && this.hasPlugin("flow"))
-      return this.finishOp(tt.braceBarR, 2);
     return this.finishOp(code === 124 ? tt.bitwiseOR : tt.bitwiseAND, 1);
   }
 

src/tokenizer/types.js

@@ -61,7 +61,7 @@ export class TokenType {
     this.isAssign = !!conf.isAssign;
     this.prefix = !!conf.prefix;
     this.postfix = !!conf.postfix;
-    this.binop = conf.binop || null;
+    this.binop = conf.binop === 0 ? 0 : conf.binop || null;
     this.updateContext = null;
   }
 }
@@ -131,6 +131,7 @@ export const types: { [name: string]: TokenType } = {
   incDec: new TokenType("++/--", { prefix, postfix, startsExpr }),
   bang: new TokenType("!", { beforeExpr, prefix, startsExpr }),
   tilde: new TokenType("~", { beforeExpr, prefix, startsExpr }),
+  pipeline: new BinopTokenType("|>", 0),
   logicalOR: new BinopTokenType("||", 1),
   logicalAND: new BinopTokenType("&&", 2),
   bitwiseOR: new BinopTokenType("|", 3),

test/fixtures/experimental/pipeline-operator/base/actual.js

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

test/fixtures/experimental/pipeline-operator/base/expected.json

@@ -0,0 +1,99 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 6,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 1,
+      "column": 6
+    }
+  },
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 6,
+    "loc": {
+      "start": {
+        "line": 1,
+        "column": 0
+      },
+      "end": {
+        "line": 1,
+        "column": 6
+      }
+    },
+    "sourceType": "script",
+    "body": [
+      {
+        "type": "ExpressionStatement",
+        "start": 0,
+        "end": 6,
+        "loc": {
+          "start": {
+            "line": 1,
+            "column": 0
+          },
+          "end": {
+            "line": 1,
+            "column": 6
+          }
+        },
+        "expression": {
+          "type": "BinaryExpression",
+          "start": 0,
+          "end": 6,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 0
+            },
+            "end": {
+              "line": 1,
+              "column": 6
+            }
+          },
+          "left": {
+            "type": "Identifier",
+            "start": 0,
+            "end": 1,
+            "loc": {
+              "start": {
+                "line": 1,
+                "column": 0
+              },
+              "end": {
+                "line": 1,
+                "column": 1
+              },
+              "identifierName": "a"
+            },
+            "name": "a"
+          },
+          "operator": "|>",
+          "right": {
+            "type": "Identifier",
+            "start": 5,
+            "end": 6,
+            "loc": {
+              "start": {
+                "line": 1,
+                "column": 5
+              },
+              "end": {
+                "line": 1,
+                "column": 6
+              },
+              "identifierName": "b"
+            },
+            "name": "b"
+          }
+        }
+      }
+    ],
+    "directives": []
+  }
+}

test/fixtures/experimental/pipeline-operator/base/options.json

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

test/fixtures/experimental/pipeline-operator/chain/actual.js

@@ -0,0 +1 @@
+x => x |> inc |> double

test/fixtures/experimental/pipeline-operator/chain/expected.json

@@ -0,0 +1,170 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 23,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 1,
+      "column": 23
+    }
+  },
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 23,
+    "loc": {
+      "start": {
+        "line": 1,
+        "column": 0
+      },
+      "end": {
+        "line": 1,
+        "column": 23
+      }
+    },
+    "sourceType": "script",
+    "body": [
+      {
+        "type": "ExpressionStatement",
+        "start": 0,
+        "end": 23,
+        "loc": {
+          "start": {
+            "line": 1,
+            "column": 0
+          },
+          "end": {
+            "line": 1,
+            "column": 23
+          }
+        },
+        "expression": {
+          "type": "ArrowFunctionExpression",
+          "start": 0,
+          "end": 23,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 0
+            },
+            "end": {
+              "line": 1,
+              "column": 23
+            }
+          },
+          "id": null,
+          "generator": false,
+          "expression": true,
+          "async": false,
+          "params": [
+            {
+              "type": "Identifier",
+              "start": 0,
+              "end": 1,
+              "loc": {
+                "start": {
+                  "line": 1,
+                  "column": 0
+                },
+                "end": {
+                  "line": 1,
+                  "column": 1
+                },
+                "identifierName": "x"
+              },
+              "name": "x"
+            }
+          ],
+          "body": {
+            "type": "BinaryExpression",
+            "start": 5,
+            "end": 23,
+            "loc": {
+              "start": {
+                "line": 1,
+                "column": 5
+              },
+              "end": {
+                "line": 1,
+                "column": 23
+              }
+            },
+            "left": {
+              "type": "BinaryExpression",
+              "start": 5,
+              "end": 13,
+              "loc": {
+                "start": {
+                  "line": 1,
+                  "column": 5
+                },
+                "end": {
+                  "line": 1,
+                  "column": 13
+                }
+              },
+              "left": {
+                "type": "Identifier",
+                "start": 5,
+                "end": 6,
+                "loc": {
+                  "start": {
+                    "line": 1,
+                    "column": 5
+                  },
+                  "end": {
+                    "line": 1,
+                    "column": 6
+                  },
+                  "identifierName": "x"
+                },
+                "name": "x"
+              },
+              "operator": "|>",
+              "right": {
+                "type": "Identifier",
+                "start": 10,
+                "end": 13,
+                "loc": {
+                  "start": {
+                    "line": 1,
+                    "column": 10
+                  },
+                  "end": {
+                    "line": 1,
+                    "column": 13
+                  },
+                  "identifierName": "inc"
+                },
+                "name": "inc"
+              }
+            },
+            "operator": "|>",
+            "right": {
+              "type": "Identifier",
+              "start": 17,
+              "end": 23,
+              "loc": {
+                "start": {
+                  "line": 1,
+                  "column": 17
+                },
+                "end": {
+                  "line": 1,
+                  "column": 23
+                },
+                "identifierName": "double"
+              },
+              "name": "double"
+            }
+          }
+        }
+      }
+    ],
+    "directives": []
+  }
+}

test/fixtures/experimental/pipeline-operator/chain/options.json

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

test/fixtures/experimental/pipeline-operator/multiline/actual.js

@@ -0,0 +1,4 @@
+let result = "hello"
+  |> doubleSay
+  |> capitalize
+  |> exclaim;