Parsing for pipe operator

commit b10a5e48d1552ff389de314762e863197bc0da7e
Author: William C. Johnson <wcjohnson@oigroup.net>
Date:   Sun Jul 16 22:55:34 2017 -0400

    Fix associativity

commit 0fac7c226b9cd9cda94a5956a45a067a145e2976
Author: William C. Johnson <wcjohnson@oigroup.net>
Date:   Sun Jul 16 22:22:34 2017 -0400

    Parse pipe operator as subscript

commit b21acb2f12941d9d7d4279320de4c55c7ee3b50f
Author: William C. Johnson <wcjohnson@oigroup.net>
Date:   Sun Jul 16 21:17:17 2017 -0400

    Basic pipeCall parsing

src/parser/expression.js

@@ -468,6 +468,13 @@ pp.parseSubscripts = function (base, startPos, startLoc, noCalls) {
       node.callee = base;
       const next = this.parseBangCall(node, "CallExpression");
       if (next) base = next; else return node;
+    } else if (
+      !noCalls &&
+      this.hasPlugin("pipeCall") &&
+      this.match(tt.pipeCall)
+    ) {
+      const node = this.startNodeAt(startPos, startLoc);
+      base = this.parsePipeCall(node, base);
     } else if (!(this.hasPlugin("lightscript") && this.isNonIndentedBreakFrom(startPos)) && this.eat(tt.bracketL)) {
       const node = this.startNodeAt(startPos, startLoc);
       node.object = base;

src/plugins/pipeCall.js

@@ -0,0 +1,26 @@
+import Parser from "../parser";
+import { types as tt, TokenType } from "../tokenizer/types";
+const pp = Parser.prototype;
+
+export default function(parser) {
+  if (parser.__pipeCallPluginInstalled) return;
+  parser.__pipeCallPluginInstalled = true;
+
+  tt.pipeCall = new TokenType("|>");
+
+  pp.parsePipeCall = function(node, left) {
+    this.next();
+
+    node.left = left;
+
+    // Left-associative parsing of pipeCalls
+    const right = this.parseExprAtom();
+    if (this.match(tt.pipeCall)) {
+      node.right = right;
+    } else {
+      node.right = this.parseSubscripts(right, this.state.start, this.state.startLoc, true);
+    }
+
+    return this.finishNode(node, "PipeCallExpression");
+  };
+}

src/registerPlugins.js

@@ -8,6 +8,7 @@ import bangCallPlugin from "./plugins/bangCall";
 import significantWhitespacePlugin from "./plugins/significantWhitespace";
 import enhancedComprehensionPlugin from "./plugins/enhancedComprehension";
 import syntacticPlaceholderPlugin from "./plugins/syntacticPlaceholder";
+import pipeCallPlugin from "./plugins/pipeCall";
 import { matchCoreSyntax, match } from "./plugins/match";
 
 function noncePlugin() {}
@@ -84,4 +85,7 @@ export default function registerPlugins(plugins, metadata) {
   // Parse identifiers beginning with `_` or another user-chosen symbol
   // as PlaceholderExpressions.
   registerPlugin("syntacticPlaceholder", syntacticPlaceholderPlugin);
+
+  // |> infix operator for piped function calls
+  registerPlugin("pipeCall", pipeCallPlugin);
 }

src/tokenizer/index.js

@@ -341,6 +341,10 @@ export default class Tokenizer {
     if (next === code) return this.finishOp(code === 124 ? tt.logicalOR : tt.logicalAND, 2);
     if (next === 61) return this.finishOp(tt.assign, 2);
     if (code === 124 && next === 125 && this.hasPlugin("flow")) return this.finishOp(tt.braceBarR, 2);
+    if (code === 124 && next === 62 && this.hasPlugin("pipeCall")) {
+      this.state.pos += 2;
+      return this.finishToken(tt.pipeCall, "|>");
+    }
     return this.finishOp(code === 124 ? tt.bitwiseOR : tt.bitwiseAND, 1);
   }
 

test/fixtures/pipe-call/basic/associativity/actual.js

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

test/fixtures/pipe-call/basic/associativity/expected.json

@@ -0,0 +1,130 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 11,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 1,
+      "column": 11
+    }
+  },
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 11,
+    "loc": {
+      "start": {
+        "line": 1,
+        "column": 0
+      },
+      "end": {
+        "line": 1,
+        "column": 11
+      }
+    },
+    "sourceType": "script",
+    "body": [
+      {
+        "type": "ExpressionStatement",
+        "start": 0,
+        "end": 11,
+        "loc": {
+          "start": {
+            "line": 1,
+            "column": 0
+          },
+          "end": {
+            "line": 1,
+            "column": 11
+          }
+        },
+        "expression": {
+          "type": "PipeCallExpression",
+          "start": 0,
+          "end": 11,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 0
+            },
+            "end": {
+              "line": 1,
+              "column": 11
+            }
+          },
+          "left": {
+            "type": "PipeCallExpression",
+            "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"
+            },
+            "right": {
+              "type": "Identifier",
+              "start": 5,
+              "end": 6,
+              "loc": {
+                "start": {
+                  "line": 1,
+                  "column": 5
+                },
+                "end": {
+                  "line": 1,
+                  "column": 6
+                },
+                "identifierName": "b"
+              },
+              "name": "b"
+            }
+          },
+          "right": {
+            "type": "Identifier",
+            "start": 10,
+            "end": 11,
+            "loc": {
+              "start": {
+                "line": 1,
+                "column": 10
+              },
+              "end": {
+                "line": 1,
+                "column": 11
+              },
+              "identifierName": "c"
+            },
+            "name": "c"
+          }
+        }
+      }
+    ],
+    "directives": []
+  }
+}

test/fixtures/pipe-call/basic/pipe/actual.js

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

test/fixtures/pipe-call/basic/pipe/expected.json

@@ -0,0 +1,98 @@
+{
+  "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": "PipeCallExpression",
+          "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"
+          },
+          "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/pipe-call/options.json

@@ -0,0 +1,8 @@
+{
+  "alternatives": {
+    "default": {
+      "allPlugins": true,
+      "excludePlugins": ["estree"]
+    }
+  }
+}