Rely on Babylon for interpreter directive parsing, instead of babel/core.

packages/babel-core/src/transformation/file/file.js

@@ -28,14 +28,12 @@ export default class File {
   metadata: {} = {};
   hub: Hub = new Hub(this);
   code: string = "";
-  shebang: string | null = "";
   inputMap: Object | null = null;
 
-  constructor(options: {}, { code, ast, shebang, inputMap }: NormalizedFile) {
+  constructor(options: {}, { code, ast, inputMap }: NormalizedFile) {
     this.opts = options;
     this.code = code;
     this.ast = ast;
-    this.shebang = shebang;
     this.inputMap = inputMap;
 
     this.path = NodePath.get({
@@ -48,6 +46,23 @@ export default class File {
     this.scope = this.path.scope;
   }
 
+  /**
+   * Provide backward-compatible access to the interpreter directive handling
+   * in Babel 6.x. If you are writing a plugin for Babel 7.x, it would be
+   * best to use 'program.interpreter' directly.
+   */
+  get shebang(): string {
+    const { interpreter } = this.path.node;
+    return interpreter ? interpreter.value : "";
+  }
+  set shebang(value: string): void {
+    if (value) {
+      this.path.get("interpreter").replaceWith(t.interpreterDirective(value));
+    } else {
+      this.path.get("interpreter").remove();
+    }
+  }
+
   set(key: mixed, val: mixed) {
     this._map.set(key, val);
   }

packages/babel-core/src/transformation/file/generate.js

@@ -14,7 +14,7 @@ export default function generateCode(
   outputCode: string,
   outputMap: SourceMap | null,
 } {
-  const { opts, ast, shebang, code, inputMap } = file;
+  const { opts, ast, code, inputMap } = file;
 
   const results = [];
   for (const plugins of pluginPasses) {
@@ -53,11 +53,6 @@ export default function generateCode(
 
   let { code: outputCode, map: outputMap } = result;
 
-  if (shebang) {
-    // add back shebang
-    outputCode = `${shebang}\n${outputCode}`;
-  }
-
   if (outputMap && inputMap) {
     outputMap = mergeSourceMap(inputMap.toObject(), outputMap);
   }

packages/babel-core/src/transformation/normalize-file.js

@@ -8,12 +8,9 @@ import { codeFrameColumns } from "@babel/code-frame";
 import File from "./file/file";
 import generateMissingPluginMessage from "./util/missing-plugin-helper";
 
-const shebangRegex = /^#!.*/;
-
 export type NormalizedFile = {
   code: string,
   ast: {},
-  shebang: string | null,
   inputMap: Converter | null,
 };
 
@@ -25,7 +22,6 @@ export default function normalizeFile(
 ): File {
   code = `${code || ""}`;
 
-  let shebang = null;
   let inputMap = null;
   if (options.inputSourceMap !== false) {
     inputMap = convertSourceMap.fromSource(code);
@@ -36,12 +32,6 @@ export default function normalizeFile(
     }
   }
 
-  const shebangMatch = shebangRegex.exec(code);
-  if (shebangMatch) {
-    shebang = shebangMatch[0];
-    code = code.replace(shebangRegex, "");
-  }
-
   if (ast) {
     if (ast.type === "Program") {
       ast = t.file(ast, [], []);
@@ -58,7 +48,6 @@ export default function normalizeFile(
   return new File(options, {
     code,
     ast,
-    shebang,
     inputMap,
   });
 }

packages/babel-core/test/api.js

@@ -370,6 +370,60 @@ describe("api", function() {
     );
   });
 
+  it("interpreter directive backward-compat", function() {
+    function doTransform(code, preHandler) {
+      return transform(code, {
+        plugins: [
+          {
+            pre: preHandler,
+          },
+        ],
+      }).code;
+    }
+
+    // Writes value properly.
+    expect(
+      doTransform("", file => {
+        file.shebang = "env node";
+      }),
+    ).toBe(`#!env node`);
+    expect(
+      doTransform("#!env node", file => {
+        file.shebang = "env node2";
+      }),
+    ).toBe(`#!env node2`);
+    expect(
+      doTransform("", file => {
+        file.shebang = "";
+      }),
+    ).toBe(``);
+    expect(
+      doTransform("#!env node", file => {
+        file.shebang = "";
+      }),
+    ).toBe(``);
+
+    // Reads value properly.
+    doTransform("", file => {
+      expect(file.shebang).toBe("");
+    });
+    doTransform("#!env node", file => {
+      expect(file.shebang).toBe("env node");
+    });
+
+    // Reads and writes properly.
+    expect(
+      doTransform("#!env node", file => {
+        expect(file.shebang).toBe("env node");
+
+        file.shebang = "env node2";
+        expect(file.shebang).toBe("env node2");
+
+        file.shebang = "env node3";
+      }),
+    ).toBe(`#!env node3`);
+  });
+
   it("source map merging", function() {
     const result = transform(
       [

packages/babel-core/test/fixtures/transformation/misc/retain-lines-interpreter-directive/output.js

@@ -1,3 +1,2 @@
 #!env node
-"use strict";
-var someFirstLine;
+"use strict";var someFirstLine;

packages/babel-core/test/fixtures/transformation/source-maps/interpreter-directive-prefix/source-map.json

@@ -1,5 +1,5 @@
 {
-  "mappings": "AAEAA,QAAQC,GAAR,CAAY,eAAZ",
+  "mappings": "AAAA;AAEAA,QAAQC,GAAR,CAAY,eAAZ",
   "names": [
     "console",
     "log"
@@ -8,7 +8,7 @@
     "source-maps/interpreter-directive-prefix/input.js"
   ],
   "sourcesContent": [
-    "\n\nconsole.log(\"Hello, world!\");"
+    "#!env node\n\nconsole.log(\"Hello, world!\");"
   ],
   "version": 3
 }