Fix wrong range format on files with BOM (#8936)

changelog_unreleased/api/pr-8936.md

@@ -0,0 +1,28 @@
+#### Fix wrong range format on files with BOM ([#8936](https://github.com/prettier/prettier/pull/8936) by [@fisker](https://github.com/fisker))
+
+When files have BOM, in previous version, the real range is wrongly calculated.
+
+<!-- prettier-ignore -->
+```js
+const text = "\uFEFF" + "foo = 1.0000;bar = 1.0000;";
+//                       ^^^^^^^^^^^^^ Range
+const result = require("prettier")
+  .format(text, {
+    parser: "babel",
+    rangeStart: 1,
+    rangeEnd: 13,
+  })
+  // Visualize BOM
+  .replace("\uFEFF", "<<BOM>>")
+  // Visualize EOL
+  .replace("\n", "<<EOL>>");
+
+console.log(result);
+
+// Prettier stable
+// -> <<BOM>>foo = 1.0;<<EOL>>bar = 1.0;
+//                            ^^^^^^^^^ This part should not be formatted
+
+// Prettier master
+// -> <<BOM>>foo = 1.0;bar = 1.0000;
+```

src/main/core.js

@@ -284,13 +284,13 @@ function format(text, opts) {
   if (hasUnicodeBOM) {
     text = text.slice(1);
     if (hasCursor) {
-      opts.cursorOffset++;
+      opts.cursorOffset--;
     }
     if (hasRangeStart) {
-      opts.rangeStart++;
+      opts.rangeStart--;
     }
     if (hasRangeEnd) {
-      opts.rangeEnd++;
+      opts.rangeEnd--;
     }
   }
 

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

@@ -0,0 +1,75 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`snippet: cursor-1.js format 1`] = `
+====================================options=====================================
+parsers: ["babel"]
+printWidth: 80
+                                                                                | printWidth
+=====================================input======================================
+(function(){return        <|>15})()
+
+=====================================output=====================================
+(function () {
+  return <|>15;
+})();
+
+================================================================================
+`;
+
+exports[`snippet: range-1.js format 1`] = `
+====================================options=====================================
+parsers: ["babel"]
+printWidth: 80
+     |                                                                                | printWidth
+=====================================input======================================
+  1 | 
+  2 | 
+> 3 | class    a {
+    |         ^^^^
+> 4 |   b(   ) {}
+    | ^^^^^^^^^^^
+  5 | }
+  6 | 
+  7 | let    x
+  8 | 
+=====================================output=====================================
+
+
+class a {
+  b() {}
+}
+
+let    x
+
+================================================================================
+`;
+
+exports[`snippet: range-and-cursor-1.js format 1`] = `
+====================================options=====================================
+parsers: ["babel"]
+printWidth: 80
+     |                                                                                | printWidth
+=====================================input======================================
+  1 | 
+  2 | 
+  3 | 
+> 4 | class    a {
+    |         ^^^^
+> 5 |   b(  <|> ) {}
+    | ^^^^^^^^^^^^^^
+  6 | }
+  7 | 
+  8 | let    x 
+  9 | 
+=====================================output=====================================
+
+
+
+class a {
+  b(<|>) {}
+}
+
+let    x 
+
+================================================================================
+`;

tests/js/bom/jsfmt.spec.js

@@ -0,0 +1,19 @@
+const fs = require("fs");
+const path = require("path");
+const fixtureDirectory = path.join(__dirname, "../eol");
+
+const snippets = fs
+  .readdirSync(fixtureDirectory)
+  .filter(
+    (fileName) => fileName !== "__snapshots__" && fileName !== "jsfmt.spec.js"
+  )
+  .map((fileName) => {
+    const file = path.join(fixtureDirectory, fileName);
+    const code = "\uFEFF" + fs.readFileSync(file, "utf8");
+    return {
+      name: fileName,
+      code,
+    };
+  });
+
+run_spec({ dirname: __dirname, snippets }, ["babel"]);