Add parsing support for the "source phase imports" proposal

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

@@ -248,6 +248,10 @@ export function ImportDeclaration(this: Printer, node: t.ImportDeclaration) {
     this.noIndentInnerCommentsHere();
     this.word("module");
     this.space();
+  } else if (node.phase) {
+    this.noIndentInnerCommentsHere();
+    this.word(node.phase);
+    this.space();
   }
 
   const specifiers = node.specifiers.slice(0);
@@ -315,6 +319,10 @@ export function ImportNamespaceSpecifier(
 
 export function ImportExpression(this: Printer, node: t.ImportExpression) {
   this.word("import");
+  if (node.phase) {
+    this.token(".");
+    this.word(node.phase);
+  }
   this.token("(");
   this.print(node.source, node);
   if (node.options != null) {

packages/babel-generator/test/fixtures/import-phases/options.json

@@ -0,0 +1,4 @@
+{
+  "plugins": ["sourcePhaseImports"],
+  "parserOpts": { "createImportExpressions": true }
+}

packages/babel-generator/test/fixtures/import-phases/source-declaration/input.js

@@ -0,0 +1 @@
+import source x from "y";

packages/babel-generator/test/fixtures/import-phases/source-declaration/output.js

@@ -0,0 +1 @@
+import source x from "y";

packages/babel-generator/test/fixtures/import-phases/source-expression/input.js

@@ -0,0 +1 @@
+import.source("x");

packages/babel-generator/test/fixtures/import-phases/source-expression/output.js

@@ -0,0 +1 @@
+import.source("x");

packages/babel-parser/data/schema.json

@@ -192,6 +192,7 @@
               "placeholders",
               "privateIn",
               "regexpUnicodeSets",
+              "sourcePhaseImports",
               "throwExpressions",
               "topLevelAwait",
               "typescript",

packages/babel-parser/src/parse-error/standard-errors.ts

@@ -233,6 +233,10 @@ export default {
     "In non-strict mode code, functions can only be declared at top level or inside a block.",
   SloppyFunctionAnnexB:
     "In non-strict mode code, functions can only be declared at top level, inside a block, or as the body of an if statement.",
+  SourcePhaseImportRequiresDefault:
+    'Only `import source x from "./module"` is valid.',
+  SourcePhaseDynamicImportRequiresImportExpressions:
+    "'import.source(...)' can only be parsed when using the 'createImportExpressions' option.",
   StaticPrototype: "Classes may not have static property named prototype.",
   SuperNotAllowed:
     "`super()` is only valid inside a class constructor of a subclass. Maybe a typo in the method name ('constructor') or not extending another class?",

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

@@ -1652,7 +1652,10 @@ export default abstract class ExpressionParser extends LValParser {
   }
 
   // https://tc39.es/ecma262/#prod-ImportMeta
-  parseImportMetaProperty(node: Undone<N.MetaProperty>): N.MetaProperty {
+  parseImportMetaProperty(
+    this: Parser,
+    node: Undone<N.MetaProperty | N.ImportExpression>,
+  ): N.MetaProperty | N.ImportExpression {
     const id = this.createIdentifier(
       this.startNodeAtNode<N.Identifier>(node),
       "import",
@@ -1664,9 +1667,20 @@ export default abstract class ExpressionParser extends LValParser {
         this.raise(Errors.ImportMetaOutsideModule, { at: id });
       }
       this.sawUnambiguousESM = true;
+    } else if (this.isContextual(tt._source)) {
+      this.expectPlugin("sourcePhaseImports");
+      if (!this.options.createImportExpressions) {
+        throw this.raise(
+          Errors.SourcePhaseDynamicImportRequiresImportExpressions,
+          { at: this.state.startLoc },
+        );
+      }
+      this.next();
+      (node as Undone<N.ImportExpression>).phase = "source";
+      return this.parseImportCall(node as Undone<N.ImportExpression>);
     }
 
-    return this.parseMetaProperty(node, id, "meta");
+    return this.parseMetaProperty(node as Undone<N.MetaProperty>, id, "meta");
   }
 
   parseLiteralAtNode<T extends N.Node>(

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

@@ -2870,13 +2870,21 @@ export default abstract class StatementParser extends ExpressionParser {
   }
 
   checkImportReflection(node: Undone<N.ImportDeclaration>) {
-    if (node.module) {
-      if (
-        node.specifiers.length !== 1 ||
-        node.specifiers[0].type !== "ImportDefaultSpecifier"
-      ) {
+    const { specifiers } = node;
+    const isSingleDefaultBinding =
+      specifiers.length === 1 &&
+      specifiers[0].type === "ImportDefaultSpecifier";
+
+    if (node.phase === "source") {
+      if (!isSingleDefaultBinding) {
+        this.raise(Errors.SourcePhaseImportRequiresDefault, {
+          at: specifiers[0].loc.start,
+        });
+      }
+    } else if (node.module) {
+      if (!isSingleDefaultBinding) {
         this.raise(Errors.ImportReflectionNotBinding, {
-          at: node.specifiers[0].loc.start,
+          at: specifiers[0].loc.start,
         });
       }
       if (node.assertions?.length > 0) {
@@ -2921,7 +2929,8 @@ export default abstract class StatementParser extends ExpressionParser {
   }
 
   isPotentialImportPhase(isExport: boolean): boolean {
-    return !isExport && this.isContextual(tt._module);
+    if (isExport) return false;
+    return this.isContextual(tt._source) || this.isContextual(tt._module);
   }
 
   applyImportPhase(
@@ -2932,20 +2941,28 @@ export default abstract class StatementParser extends ExpressionParser {
   ): void {
     if (isExport) {
       if (!process.env.IS_PUBLISH) {
-        if (phase === "module") {
+        if (phase === "module" || phase === "source") {
           throw new Error(
-            "Assertion failure: export declarations do not support the 'module' phase.",
+            `Assertion failure: export declarations do not support the '${phase}' phase.`,
           );
         }
       }
       return;
     }
+
     if (phase === "module") {
       this.expectPlugin("importReflection", loc);
       (node as N.ImportDeclaration).module = true;
     } else if (this.hasPlugin("importReflection")) {
       (node as N.ImportDeclaration).module = false;
     }
+
+    if (phase === "source") {
+      this.expectPlugin("sourcePhaseImports", loc);
+      (node as N.ImportDeclaration).phase = "source";
+    } else if (this.hasPlugin("sourcePhaseImports")) {
+      (node as N.ImportDeclaration).phase = null;
+    }
   }
 
   /*

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

@@ -291,6 +291,7 @@ export const tt = {
   _of: createKeywordLike("of", { startsExpr }),
   _sent: createKeywordLike("sent", { startsExpr }),
   _set: createKeywordLike("set", { startsExpr }),
+  _source: createKeywordLike("source", { startsExpr }),
   _static: createKeywordLike("static", { startsExpr }),
   _using: createKeywordLike("using", { startsExpr }),
   _yield: createKeywordLike("yield", { startsExpr }),

packages/babel-parser/src/types.d.ts

@@ -627,6 +627,7 @@ export interface NewExpression extends CallOrNewBase {
 export interface ImportExpression extends NodeBase {
   type: "ImportExpression";
   source: Expression;
+  phase?: null | "source";
   options: Expression | null;
 }
 
@@ -927,6 +928,7 @@ export interface ImportDeclaration extends NodeBase {
   >;
   source: Literal;
   importKind?: "type" | "typeof" | "value"; // TODO: Not in spec,
+  phase?: null | "source";
   attributes?: ImportAttribute[];
   // @deprecated
   assertions?: ImportAttribute[];

packages/babel-parser/src/typings.d.ts

@@ -36,6 +36,7 @@ export type Plugin =
   | "placeholders"
   | "privateIn" // Enabled by default
   | "regexpUnicodeSets" // Enabled by default
+  | "sourcePhaseImports"
   | "throwExpressions"
   | "topLevelAwait"
   | "v8intrinsic"

packages/babel-parser/test/fixtures/experimental/source-phase-imports/attributes-declaration/input.js

@@ -0,0 +1 @@
+import source s from "x" with { attr: "val" };

packages/babel-parser/test/fixtures/experimental/source-phase-imports/attributes-declaration/options.json

@@ -0,0 +1,4 @@
+{
+  "sourceType": "module",
+  "plugins": ["sourcePhaseImports", "importAttributes"]
+}

packages/babel-parser/test/fixtures/experimental/source-phase-imports/attributes-declaration/output.json

@@ -0,0 +1,58 @@
+{
+  "type": "File",
+  "start":0,"end":46,"loc":{"start":{"line":1,"column":0,"index":0},"end":{"line":1,"column":46,"index":46}},
+  "program": {
+    "type": "Program",
+    "start":0,"end":46,"loc":{"start":{"line":1,"column":0,"index":0},"end":{"line":1,"column":46,"index":46}},
+    "sourceType": "module",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "ImportDeclaration",
+        "start":0,"end":46,"loc":{"start":{"line":1,"column":0,"index":0},"end":{"line":1,"column":46,"index":46}},
+        "phase": "source",
+        "specifiers": [
+          {
+            "type": "ImportDefaultSpecifier",
+            "start":14,"end":15,"loc":{"start":{"line":1,"column":14,"index":14},"end":{"line":1,"column":15,"index":15}},
+            "local": {
+              "type": "Identifier",
+              "start":14,"end":15,"loc":{"start":{"line":1,"column":14,"index":14},"end":{"line":1,"column":15,"index":15},"identifierName":"s"},
+              "name": "s"
+            }
+          }
+        ],
+        "source": {
+          "type": "StringLiteral",
+          "start":21,"end":24,"loc":{"start":{"line":1,"column":21,"index":21},"end":{"line":1,"column":24,"index":24}},
+          "extra": {
+            "rawValue": "x",
+            "raw": "\"x\""
+          },
+          "value": "x"
+        },
+        "attributes": [
+          {
+            "type": "ImportAttribute",
+            "start":32,"end":43,"loc":{"start":{"line":1,"column":32,"index":32},"end":{"line":1,"column":43,"index":43}},
+            "key": {
+              "type": "Identifier",
+              "start":32,"end":36,"loc":{"start":{"line":1,"column":32,"index":32},"end":{"line":1,"column":36,"index":36},"identifierName":"attr"},
+              "name": "attr"
+            },
+            "value": {
+              "type": "StringLiteral",
+              "start":38,"end":43,"loc":{"start":{"line":1,"column":38,"index":38},"end":{"line":1,"column":43,"index":43}},
+              "extra": {
+                "rawValue": "val",
+                "raw": "\"val\""
+              },
+              "value": "val"
+            }
+          }
+        ]
+      }
+    ],
+    "directives": []
+  }
+}

packages/babel-parser/test/fixtures/experimental/source-phase-imports/attributes-expression/input.js

@@ -0,0 +1 @@
+import.source("x", { with: { attr: "val" } });

packages/babel-parser/test/fixtures/experimental/source-phase-imports/attributes-expression/options.json

@@ -0,0 +1,4 @@
+{
+  "plugins": ["sourcePhaseImports", "importAttributes"],
+  "createImportExpressions": true
+}

packages/babel-parser/test/fixtures/experimental/source-phase-imports/attributes-expression/output.json

@@ -0,0 +1,76 @@
+{
+  "type": "File",
+  "start":0,"end":46,"loc":{"start":{"line":1,"column":0,"index":0},"end":{"line":1,"column":46,"index":46}},
+  "program": {
+    "type": "Program",
+    "start":0,"end":46,"loc":{"start":{"line":1,"column":0,"index":0},"end":{"line":1,"column":46,"index":46}},
+    "sourceType": "module",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "ExpressionStatement",
+        "start":0,"end":46,"loc":{"start":{"line":1,"column":0,"index":0},"end":{"line":1,"column":46,"index":46}},
+        "expression": {
+          "type": "ImportExpression",
+          "start":0,"end":45,"loc":{"start":{"line":1,"column":0,"index":0},"end":{"line":1,"column":45,"index":45}},
+          "phase": "source",
+          "source": {
+            "type": "StringLiteral",
+            "start":14,"end":17,"loc":{"start":{"line":1,"column":14,"index":14},"end":{"line":1,"column":17,"index":17}},
+            "extra": {
+              "rawValue": "x",
+              "raw": "\"x\""
+            },
+            "value": "x"
+          },
+          "options": {
+            "type": "ObjectExpression",
+            "start":19,"end":44,"loc":{"start":{"line":1,"column":19,"index":19},"end":{"line":1,"column":44,"index":44}},
+            "properties": [
+              {
+                "type": "ObjectProperty",
+                "start":21,"end":42,"loc":{"start":{"line":1,"column":21,"index":21},"end":{"line":1,"column":42,"index":42}},
+                "method": false,
+                "key": {
+                  "type": "Identifier",
+                  "start":21,"end":25,"loc":{"start":{"line":1,"column":21,"index":21},"end":{"line":1,"column":25,"index":25},"identifierName":"with"},
+                  "name": "with"
+                },
+                "computed": false,
+                "shorthand": false,
+                "value": {
+                  "type": "ObjectExpression",
+                  "start":27,"end":42,"loc":{"start":{"line":1,"column":27,"index":27},"end":{"line":1,"column":42,"index":42}},
+                  "properties": [
+                    {
+                      "type": "ObjectProperty",
+                      "start":29,"end":40,"loc":{"start":{"line":1,"column":29,"index":29},"end":{"line":1,"column":40,"index":40}},
+                      "method": false,
+                      "key": {
+                        "type": "Identifier",
+                        "start":29,"end":33,"loc":{"start":{"line":1,"column":29,"index":29},"end":{"line":1,"column":33,"index":33},"identifierName":"attr"},
+                        "name": "attr"
+                      },
+                      "computed": false,
+                      "shorthand": false,
+                      "value": {
+                        "type": "StringLiteral",
+                        "start":35,"end":40,"loc":{"start":{"line":1,"column":35,"index":35},"end":{"line":1,"column":40,"index":40}},
+                        "extra": {
+                          "rawValue": "val",
+                          "raw": "\"val\""
+                        },
+                        "value": "val"
+                      }
+                    }
+                  ]
+                }
+              }
+            ]
+          }
+        }
+      }
+    ],
+    "directives": []
+  }
+}

packages/babel-parser/test/fixtures/experimental/source-phase-imports/dynamic-import-no-createImportExpressions/input.js

@@ -0,0 +1 @@
+import.source("foo");

packages/babel-parser/test/fixtures/experimental/source-phase-imports/dynamic-import-no-createImportExpressions/options.json

@@ -0,0 +1,4 @@
+{
+  "plugins": ["sourcePhaseImports"],
+  "throws": "'import.source(...)' can only be parsed when using the 'createImportExpressions' option. (1:7)"
+}

packages/babel-parser/test/fixtures/experimental/source-phase-imports/dynamic-import/input.js

@@ -0,0 +1 @@
+import.source("foo");

packages/babel-parser/test/fixtures/experimental/source-phase-imports/dynamic-import/options.json

@@ -0,0 +1,4 @@
+{
+  "plugins": ["sourcePhaseImports"],
+  "createImportExpressions": true
+}

packages/babel-parser/test/fixtures/experimental/source-phase-imports/dynamic-import/output.json

@@ -0,0 +1,31 @@
+{
+  "type": "File",
+  "start":0,"end":21,"loc":{"start":{"line":1,"column":0,"index":0},"end":{"line":1,"column":21,"index":21}},
+  "program": {
+    "type": "Program",
+    "start":0,"end":21,"loc":{"start":{"line":1,"column":0,"index":0},"end":{"line":1,"column":21,"index":21}},
+    "sourceType": "module",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "ExpressionStatement",
+        "start":0,"end":21,"loc":{"start":{"line":1,"column":0,"index":0},"end":{"line":1,"column":21,"index":21}},
+        "expression": {
+          "type": "ImportExpression",
+          "start":0,"end":20,"loc":{"start":{"line":1,"column":0,"index":0},"end":{"line":1,"column":20,"index":20}},
+          "phase": "source",
+          "source": {
+            "type": "StringLiteral",
+            "start":14,"end":19,"loc":{"start":{"line":1,"column":14,"index":14},"end":{"line":1,"column":19,"index":19}},
+            "extra": {
+              "rawValue": "foo",
+              "raw": "\"foo\""
+            },
+            "value": "foo"
+          }
+        }
+      }
+    ],
+    "directives": []
+  }
+}

packages/babel-parser/test/fixtures/experimental/source-phase-imports/import-default-binding-source/input.js

@@ -0,0 +1 @@
+import source from "x";