Fix empty files with shebang (#8414)

src/common/parser-include-shebang.js

@@ -1,15 +1,18 @@
 "use strict";
 
+const { getShebang } = require("./util");
+
 function includeShebang(text, ast) {
-  if (!text.startsWith("#!")) {
+  const shebang = getShebang(text);
+
+  if (!shebang) {
     return;
   }
+  const index = shebang.length;
 
-  const index = text.indexOf("\n");
-  const shebang = text.slice(2, index);
   const comment = {
     type: "Line",
-    value: shebang,
+    value: shebang.slice(2),
     range: [0, index],
     loc: {
       start: {

src/common/util.js

@@ -844,6 +844,17 @@ function isFrontMatterNode(node) {
   return node && node.type === "front-matter";
 }
 
+function getShebang(text) {
+  if (!text.startsWith("#!")) {
+    return "";
+  }
+  const index = text.indexOf("\n");
+  if (index === -1) {
+    return text;
+  }
+  return text.slice(0, index);
+}
+
 module.exports = {
   replaceEndOfLineWith,
   getStringWidth,
@@ -889,4 +900,5 @@ module.exports = {
   addTrailingComment,
   isWithinParentArrayProperty,
   isFrontMatterNode,
+  getShebang,
 };

src/language-js/pragma.js

@@ -1,18 +1,7 @@
 "use strict";
 
 const docblock = require("jest-docblock");
-
-// Logic from `/src/common/parser-include-shebang.js`
-function getShebang(text) {
-  if (!text.startsWith("#!")) {
-    return "";
-  }
-  const index = text.indexOf("\n");
-  if (index === -1) {
-    return "";
-  }
-  return text.slice(0, index);
-}
+const { getShebang } = require("../common/util");
 
 function hasPragma(text) {
   const shebang = getShebang(text);

tests/js/shebang/__snapshots__/jsfmt.spec.js.snap

@@ -33,3 +33,30 @@ function a() {}
 
 ================================================================================
 `;
+
+exports[`snippet: Empty file with shebang format 1`] = `
+====================================options=====================================
+parsers: ["babel", "flow", "typescript"]
+printWidth: 80
+                                                                                | printWidth
+=====================================input======================================
+#!/usr/bin/env node
+=====================================output=====================================
+#!/usr/bin/env node
+
+================================================================================
+`;
+
+exports[`snippet: Empty file with shebang format 2`] = `
+====================================options=====================================
+parsers: ["babel", "flow", "typescript"]
+printWidth: 80
+                                                                                | printWidth
+=====================================input======================================
+#!/usr/bin/env node
+
+=====================================output=====================================
+#!/usr/bin/env node
+
+================================================================================
+`;

tests/js/shebang/jsfmt.spec.js

@@ -1 +1,16 @@
-run_spec(__dirname, ["babel", "flow", "typescript"]);
+run_spec(
+  {
+    dirname: __dirname,
+    snippets: [
+      {
+        name: "Empty file with shebang",
+        code: "#!/usr/bin/env node",
+      },
+      {
+        name: "Empty file with shebang",
+        code: "#!/usr/bin/env node\n",
+      },
+    ],
+  },
+  ["babel", "flow", "typescript"]
+);