Support passing diff options to React components

packages/diffs/src/components/FileDiff.ts

@@ -531,7 +531,7 @@ export class FileDiff<LAnnotation = undefined> {
       this.fileDiff =
         fileDiff ??
         (oldFile != null && newFile != null
-          ? parseDiffFromFile(oldFile, newFile)
+          ? parseDiffFromFile(oldFile, newFile, this.options.diffOptions)
           : undefined);
 
       this.hunksRenderer.hydrate(this.fileDiff);
@@ -649,7 +649,11 @@ export class FileDiff<LAnnotation = undefined> {
       this.fileDiff = fileDiff;
     } else if (oldFile != null && newFile != null && filesDidChange) {
       diffDidChange = true;
-      this.fileDiff = parseDiffFromFile(oldFile, newFile);
+      this.fileDiff = parseDiffFromFile(
+        oldFile,
+        newFile,
+        this.options.diffOptions
+      );
     }
 
     if (lineAnnotations != null) {

packages/diffs/src/components/VirtualizedFileDiff.ts

@@ -347,11 +347,7 @@ export class VirtualizedFileDiff<
     this.fileDiff ??=
       fileDiff ??
       (oldFile != null && newFile != null
-        ? // NOTE(amadeus): We might be forcing ourselves to double up the
-          // computation of fileDiff (in the super.render() call), so we might want
-          // to figure out a way to avoid that.  That also could be just as simple as
-          // passing through fileDiff though... so maybe we good?
-          parseDiffFromFile(oldFile, newFile)
+        ? parseDiffFromFile(oldFile, newFile, this.options.diffOptions)
         : undefined);
 
     fileContainer = this.getOrCreateFileContainer(fileContainer);

packages/diffs/src/ssr/preloadDiffs.ts

@@ -36,7 +36,7 @@ export async function preloadDiffHTML<LAnnotation = undefined>({
   annotations,
 }: PreloadDiffOptions<LAnnotation>): Promise<string> {
   if (fileDiff == null && oldFile != null && newFile != null) {
-    fileDiff = parseDiffFromFile(oldFile, newFile);
+    fileDiff = parseDiffFromFile(oldFile, newFile, options?.diffOptions);
   }
   if (fileDiff == null) {
     throw new Error(

packages/diffs/src/types.ts

@@ -1,3 +1,4 @@
+import type { CreatePatchOptionsNonabortable } from 'diff';
 import type { ElementContent } from 'hast';
 import type {
   BundledLanguage,
@@ -393,10 +394,25 @@ export interface BaseDiffOptions extends BaseCodeOptions {
 
   // How many lines to expand per click
   expansionLineCount?: number; // 100 is default
+
+  /**
+   * Options forwarded to the underlying diff algorithm when computing diffs
+   * from file contents (oldFile/newFile). Has no effect on pre-parsed patches.
+   *
+   * Supported options:
+   * - `ignoreWhitespace`: treat lines differing only in whitespace as unchanged
+   * - `stripTrailingCr`: strip `\r` before diffing (useful for UNIX vs Windows)
+   */
+  diffOptions?: DiffComputeOptions;
 }
 
+export type DiffComputeOptions = Pick<
+  CreatePatchOptionsNonabortable,
+  'ignoreWhitespace' | 'stripTrailingCr'
+>;
+
 export type BaseDiffOptionsWithDefaults = Required<
-  Omit<BaseDiffOptions, 'unsafeCSS' | 'preferredHighlighter'>
+  Omit<BaseDiffOptions, 'unsafeCSS' | 'preferredHighlighter' | 'diffOptions'>
 >;
 
 export type CustomPreProperties = Record<string, string | number | undefined>;

packages/diffs/src/utils/areOptionsEqual.ts

@@ -1,17 +1,35 @@
 import type { FileDiffOptions } from '../components/FileDiff';
 import { DEFAULT_THEMES } from '../constants';
 import type { FileOptions } from '../react';
+import type { DiffComputeOptions } from '../types';
 import { areObjectsEqual } from './areObjectsEqual';
 import { areThemesEqual } from './areThemesEqual';
 
+type AnyOptions<L> = FileOptions<L> | FileDiffOptions<L> | undefined;
+
 export function areOptionsEqual<LAnnotation>(
-  optionsA: FileOptions<LAnnotation> | FileDiffOptions<LAnnotation> | undefined,
-  optionsB: FileOptions<LAnnotation> | FileDiffOptions<LAnnotation> | undefined
+  optionsA: AnyOptions<LAnnotation>,
+  optionsB: AnyOptions<LAnnotation>
 ): boolean {
   const themeA = optionsA?.theme ?? DEFAULT_THEMES;
   const themeB = optionsB?.theme ?? DEFAULT_THEMES;
+  const diffOptsA = getDiffOptions(optionsA);
+  const diffOptsB = getDiffOptions(optionsB);
   return (
     areThemesEqual(themeA, themeB) &&
-    areObjectsEqual(optionsA, optionsB, ['theme'])
+    areObjectsEqual(optionsA, optionsB, [
+      'theme',
+      'diffOptions' as keyof typeof optionsA,
+    ]) &&
+    areObjectsEqual(diffOptsA ?? {}, diffOptsB ?? {})
   );
 }
+
+function getDiffOptions<L>(
+  options: AnyOptions<L>
+): DiffComputeOptions | undefined {
+  if (options != null && 'diffOptions' in options) {
+    return options.diffOptions;
+  }
+  return undefined;
+}

packages/diffs/test/parseDiffFromFile.test.ts

@@ -35,4 +35,23 @@ describe('parseDiffFromFile', () => {
     const expectedNewLineCount = fileNew.split(/(?<=\n)/).length;
     expect(result.additionLines.length).toBe(expectedNewLineCount);
   });
+
+  test('ignoreWhitespace hides leading/trailing whitespace changes', () => {
+    const oldFile = {
+      name: 'test.txt',
+      contents: 'hello world\nfoo bar\n',
+    };
+    const newFile = {
+      name: 'test.txt',
+      contents: '  hello world\nfoo bar\n',
+    };
+
+    const withWhitespace = parseDiffFromFile(oldFile, newFile);
+    expect(withWhitespace.hunks.length).toBeGreaterThan(0);
+
+    const withoutWhitespace = parseDiffFromFile(oldFile, newFile, {
+      ignoreWhitespace: true,
+    });
+    expect(withoutWhitespace.hunks).toHaveLength(0);
+  });
 });