Create parser plugin "topLevelAwait" (#10449)

* Create parser plugin "topLevelAwait" * Update test262 whitelist * Update ts typings * Fix "sourceType: unambiguous" with TLA * Ambiguous tokens after await * Update await %x(0) * typo [skip ci] * Typo [skip ci] Co-Authored-By: Brian Ng <bng412@gmail.com>
babel · Oct 29, 2019 · 143d159 · 143d159
1 parent 63f9a3c
commit 143d159
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Showing 42 changed files with 2,108 additions and 461 deletions.
diff --git a/packages/babel-parser/src/index.js b/packages/babel-parser/src/index.js
@@ -25,15 +25,32 @@ export function parse(input: string, options?: Options): File {
       const parser = getParser(options, input);
       const ast = parser.parse();
 
-      // Rather than try to parse as a script first, we opt to parse as a module and convert back
-      // to a script where possible to avoid having to do a full re-parse of the input content.
-      if (!parser.sawUnambiguousESM) ast.program.sourceType = "script";
+      if (parser.sawUnambiguousESM) {
+        return ast;
+      }
+
+      if (parser.ambiguousScriptDifferentAst) {
+        // Top level await introduces code which can be both a valid script and
+        // a valid module, but which produces different ASTs:
+        //    await
+        //    0
+        // can be parsed either as an AwaitExpression, or as two ExpressionStatements.
+        try {
+          options.sourceType = "script";
+          return getParser(options, input).parse();
+        } catch {}
+      } else {
+        // This is both a valid module and a valid script, but
+        // we parse it as a script by default
+        ast.program.sourceType = "script";
+      }
+
       return ast;
     } catch (moduleError) {
       try {
         options.sourceType = "script";
         return getParser(options, input).parse();
-      } catch (scriptError) {}
+      } catch {}
 
       throw moduleError;
     }

diff --git a/packages/babel-parser/src/parser/base.js b/packages/babel-parser/src/parser/base.js
@@ -13,6 +13,7 @@ export default class BaseParser {
   plugins: PluginsMap;
   filename: ?string;
   sawUnambiguousESM: boolean = false;
+  ambiguousScriptDifferentAst: boolean = false;
 
   // Initialized by Tokenizer
   state: State;

diff --git a/packages/babel-parser/src/parser/expression.js b/packages/babel-parser/src/parser/expression.js
@@ -2208,6 +2208,7 @@ export default class ExpressionParser extends LValParser {
   isAwaitAllowed(): boolean {
     if (this.scope.inFunction) return this.scope.inAsync;
     if (this.options.allowAwaitOutsideFunction) return true;
+    if (this.hasPlugin("topLevelAwait")) return this.inModule;
     return false;
   }
 
@@ -2234,9 +2235,33 @@ export default class ExpressionParser extends LValParser {
       );
     }
 
+    if (!this.scope.inFunction && !this.options.allowAwaitOutsideFunction) {
+      if (
+        this.hasPrecedingLineBreak() ||
+        // All the following expressions are ambiguous:
+        //   await + 0, await - 0, await ( 0 ), await [ 0 ], await / 0 /u, await ``
+        this.match(tt.plusMin) ||
+        this.match(tt.parenL) ||
+        this.match(tt.bracketL) ||
+        this.match(tt.backQuote) ||
+        // Sometimes the tokenizer generates tt.slash for regexps, and this is
+        // handler by parseExprAtom
+        this.match(tt.regexp) ||
+        this.match(tt.slash) ||
+        // This code could be parsed both as a modulo operator or as an intrinsic:
+        //   await %x(0)
+        (this.hasPlugin("v8intrinsic") && this.match(tt.modulo))
+      ) {
+        this.ambiguousScriptDifferentAst = true;
+      } else {
+        this.sawUnambiguousESM = true;
+      }
+    }
+
     if (!this.state.soloAwait) {
       node.argument = this.parseMaybeUnary();
     }
+
     return this.finishNode(node, "AwaitExpression");
   }
 

diff --git a/packages/babel-parser/src/parser/statement.js b/packages/babel-parser/src/parser/statement.js
@@ -495,11 +495,7 @@ export default class StatementParser extends ExpressionParser {
     this.state.labels.push(loopLabel);
 
     let awaitAt = -1;
-    if (
-      (this.scope.inAsync ||
-        (!this.scope.inFunction && this.options.allowAwaitOutsideFunction)) &&
-      this.eatContextual("await")
-    ) {
+    if (this.isAwaitAllowed() && this.eatContextual("await")) {
       awaitAt = this.state.lastTokStart;
     }
     this.scope.enter(SCOPE_OTHER);

diff --git a/packages/babel-parser/test/fixtures/experimental/top-level-await/export-default/input.js b/packages/babel-parser/test/fixtures/experimental/top-level-await/export-default/input.js
@@ -0,0 +1 @@
+export default await 0;
diff --git a/packages/babel-parser/test/fixtures/experimental/top-level-await/export-default/options.json b/packages/babel-parser/test/fixtures/experimental/top-level-await/export-default/options.json
@@ -0,0 +1,4 @@
+{
+  "plugins": ["topLevelAwait"],
+  "sourceType": "module"
+}
diff --git a/packages/babel-parser/test/fixtures/experimental/top-level-await/export-default/output.json b/packages/babel-parser/test/fixtures/experimental/top-level-await/export-default/output.json
@@ -0,0 +1,85 @@
+{
+  "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": "module",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "ExportDefaultDeclaration",
+        "start": 0,
+        "end": 23,
+        "loc": {
+          "start": {
+            "line": 1,
+            "column": 0
+          },
+          "end": {
+            "line": 1,
+            "column": 23
+          }
+        },
+        "declaration": {
+          "type": "AwaitExpression",
+          "start": 15,
+          "end": 22,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 15
+            },
+            "end": {
+              "line": 1,
+              "column": 22
+            }
+          },
+          "argument": {
+            "type": "NumericLiteral",
+            "start": 21,
+            "end": 22,
+            "loc": {
+              "start": {
+                "line": 1,
+                "column": 21
+              },
+              "end": {
+                "line": 1,
+                "column": 22
+              }
+            },
+            "extra": {
+              "rawValue": 0,
+              "raw": "0"
+            },
+            "value": 0
+          }
+        }
+      }
+    ],
+    "directives": []
+  }
+}
diff --git a/packages/babel-parser/test/fixtures/experimental/top-level-await/for-await-module/input.js b/packages/babel-parser/test/fixtures/experimental/top-level-await/for-await-module/input.js
@@ -0,0 +1 @@
+for await (const a of b);
diff --git a/...ges/babel-parser/test/fixtures/experimental/top-level-await/for-await-module/options.json b/...ges/babel-parser/test/fixtures/experimental/top-level-await/for-await-module/options.json
@@ -0,0 +1,4 @@
+{
+  "plugins": ["topLevelAwait"],
+  "sourceType": "module"
+}
diff --git a/...ages/babel-parser/test/fixtures/experimental/top-level-await/for-await-module/output.json b/...ages/babel-parser/test/fixtures/experimental/top-level-await/for-await-module/output.json
@@ -0,0 +1,134 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 25,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 1,
+      "column": 25
+    }
+  },
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 25,
+    "loc": {
+      "start": {
+        "line": 1,
+        "column": 0
+      },
+      "end": {
+        "line": 1,
+        "column": 25
+      }
+    },
+    "sourceType": "module",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "ForOfStatement",
+        "start": 0,
+        "end": 25,
+        "loc": {
+          "start": {
+            "line": 1,
+            "column": 0
+          },
+          "end": {
+            "line": 1,
+            "column": 25
+          }
+        },
+        "await": true,
+        "left": {
+          "type": "VariableDeclaration",
+          "start": 11,
+          "end": 18,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 11
+            },
+            "end": {
+              "line": 1,
+              "column": 18
+            }
+          },
+          "declarations": [
+            {
+              "type": "VariableDeclarator",
+              "start": 17,
+              "end": 18,
+              "loc": {
+                "start": {
+                  "line": 1,
+                  "column": 17
+                },
+                "end": {
+                  "line": 1,
+                  "column": 18
+                }
+              },
+              "id": {
+                "type": "Identifier",
+                "start": 17,
+                "end": 18,
+                "loc": {
+                  "start": {
+                    "line": 1,
+                    "column": 17
+                  },
+                  "end": {
+                    "line": 1,
+                    "column": 18
+                  },
+                  "identifierName": "a"
+                },
+                "name": "a"
+              },
+              "init": null
+            }
+          ],
+          "kind": "const"
+        },
+        "right": {
+          "type": "Identifier",
+          "start": 22,
+          "end": 23,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 22
+            },
+            "end": {
+              "line": 1,
+              "column": 23
+            },
+            "identifierName": "b"
+          },
+          "name": "b"
+        },
+        "body": {
+          "type": "EmptyStatement",
+          "start": 24,
+          "end": 25,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 24
+            },
+            "end": {
+              "line": 1,
+              "column": 25
+            }
+          }
+        }
+      }
+    ],
+    "directives": []
+  }
+}
diff --git a/packages/babel-parser/test/fixtures/experimental/top-level-await/for-await-script/input.js b/packages/babel-parser/test/fixtures/experimental/top-level-await/for-await-script/input.js
@@ -0,0 +1 @@
+for await (const a of b);
diff --git a/...ges/babel-parser/test/fixtures/experimental/top-level-await/for-await-script/options.json b/...ges/babel-parser/test/fixtures/experimental/top-level-await/for-await-script/options.json
@@ -0,0 +1,5 @@
+{
+  "plugins": ["topLevelAwait"],
+  "sourceType": "script",
+  "throws": "Unexpected token, expected \"(\" (1:4)"
+}
diff --git a/packages/babel-parser/test/fixtures/experimental/top-level-await/inside-arrow/input.js b/packages/babel-parser/test/fixtures/experimental/top-level-await/inside-arrow/input.js
@@ -0,0 +1 @@
+() => await 0;
diff --git a/packages/babel-parser/test/fixtures/experimental/top-level-await/inside-arrow/options.json b/packages/babel-parser/test/fixtures/experimental/top-level-await/inside-arrow/options.json
@@ -0,0 +1,5 @@
+{
+  "plugins": ["topLevelAwait"],
+  "sourceType": "module",
+  "throws": "Can not use keyword 'await' outside an async function (1:6)"
+}
diff --git a/packages/babel-parser/test/fixtures/experimental/top-level-await/inside-block/input.js b/packages/babel-parser/test/fixtures/experimental/top-level-await/inside-block/input.js
@@ -0,0 +1,3 @@
+if (true) {
+  await 0;
+}
diff --git a/packages/babel-parser/test/fixtures/experimental/top-level-await/inside-block/options.json b/packages/babel-parser/test/fixtures/experimental/top-level-await/inside-block/options.json
@@ -0,0 +1,4 @@
+{
+  "plugins": ["topLevelAwait"],
+  "sourceType": "module"
+}