chore: minimizeDiff follow-ups (size cap, trailing commas, snapshots)

packages/sv-utils/src/sanitize.ts

@@ -28,34 +28,28 @@ export function sanitizeName(name: string, style: 'package' | 'wrangler'): strin
 	return sanitized || 'undefined-sv-name';
 }
 
+// `diffLines` is O(N·D); past this size we keep the printer output rather than hanging.
+const MAX_DIFF_INPUT_BYTES = 512 * 1024;
+
 /**
- * Minimizes formatting churn in generated output.
- *
- * Formatting-only hunks are restored verbatim from the original. Real changes keep the updated
- * content while reusing the original blank-line layout when the old and updated lines can be paired
- * safely. This avoids unrelated punctuation and blank-line churn around useful edits without
- * rewriting authored content.
- *
- * Brand-new or whitespace-only files are kept verbatim: their blank lines are authored layout, not
- * printer churn, so stripping them would mangle generated markdown, env files, etc.
+ * Minimizes formatting churn in reprinted output: formatting-only hunks are restored verbatim from
+ * the original, real changes keep the updated content but reuse the original blank-line layout.
  */
 export function minimizeDiff(old: string, updated: string): string {
 	if (isBlank(old)) return updated;
+	if (old.length > MAX_DIFF_INPUT_BYTES || updated.length > MAX_DIFF_INPUT_BYTES) return updated;
 
 	const original = normalizeLineEndings(old);
 	const replacement = normalizeLineEndings(updated);
 
-	// These passes need different line alignment. First restore formatting-only replacements using
-	// exact lines, then ignore indentation while restoring the original blank-line layout.
 	const formattingMinimized = restoreFormattingOnlyChanges(original, replacement);
 	return restoreBlankLineLayout(original, formattingMinimized);
 }
 
 type LineChange = ReturnType<typeof diffLines>[number];
 
 function restoreFormattingOnlyChanges(original: string, replacement: string): string {
-	// Exact matching keeps closing braces and other repeated punctuation attached to the replacement
-	// that reformatted them instead of letting diffLines use them as misleading anchors.
+	// exact matching keeps reformatted punctuation inside the hunk instead of becoming a false anchor
 	const changes = diffLines(original, replacement);
 	let result = '';
 
@@ -78,8 +72,7 @@ function restoreFormattingOnlyChanges(original: string, replacement: string): st
 }
 
 function restoreBlankLineLayout(original: string, replacement: string): string {
-	// The formatting pass has already handled rewrapped hunks. Ignoring whitespace here gives
-	// diffLines stable anchors across reindentation so isolated blank-line moves remain visible.
+	// ignoring whitespace keeps reindented lines as anchors so only blank-line moves show up
 	const changes = diffLines(original, replacement, { ignoreWhitespace: true });
 	let result = '';
 
@@ -94,8 +87,7 @@ function restoreBlankLineLayout(original: string, replacement: string): string {
 			continue;
 		}
 
-		// diffLines can use a blank line as an anchor between the removed and added sides of a
-		// replacement. Consider that anchor as part of the hunk so the decision is still made here.
+		// a blank line can anchor between the removed and added sides; treat it as part of the hunk
 		if (
 			isChange(change) &&
 			next &&
@@ -112,7 +104,6 @@ function restoreBlankLineLayout(original: string, replacement: string): string {
 		if (!isChange(change)) {
 			result += change.value;
 		} else if (isBlank(change.value)) {
-			// Keep removed blank lines and discard added ones.
 			if (change.removed) result += change.value;
 		} else if (change.added) {
 			result += change.value;
@@ -141,9 +132,6 @@ function isBlank(value: string): boolean {
 }
 
 function resolveReplacement(changes: LineChange[]): string {
-	// Reconstruct both sides because a replacement may include an unchanged blank-line anchor.
-	// Formatting-equivalent replacements use the original verbatim; real edits keep their updated
-	// content while borrowing the original blank-line positions when the lines pair safely.
 	let original = '';
 	let replacement = '';
 
@@ -161,7 +149,7 @@ function normalizeForComparison(value: string): string {
 	return value
 		.replace(/\s/g, '')
 		.replace(/;/g, '')
-		.replace(/,([}\]])/g, '$1')
+		.replace(/,([}\])])/g, '$1')
 		.replace(/,$/, '');
 }
 
@@ -170,7 +158,7 @@ function preserveBlankLineLayout(original: string, replacement: string): string
 	const replacementLines = replacement.split('\n');
 	const replacementContent = replacementLines.filter((line) => line.trim() !== '');
 
-	// Positional pairing is only safe when every original content line has an updated counterpart.
+	// positional pairing is only safe when content line counts match
 	if (originalLines.filter((line) => line.trim() !== '').length !== replacementContent.length) {
 		return replacement;
 	}

packages/sv-utils/src/tests/sanitize.ts

@@ -580,6 +580,37 @@ describe('minimizeDiff', () => {
 		expect(minimizeDiff(old, updated)).toBe(old.replace("'old'", "'new'"));
 	});
 
+	it('restores original formatting when a call with trailing commas is collapsed onto one line', () => {
+		const old = dedent`
+			const version = 'old';
+
+			const sha = await canonicalize(
+				opts.owner,
+				opts.repo,
+				opts.commit,
+			);
+		`;
+
+		const updated = dedent`
+			const version = 'new';
+
+			const sha = await canonicalize(opts.owner, opts.repo, opts.commit);
+		`;
+
+		expect(minimizeDiff(old, updated)).toBe(old.replace("'old'", "'new'"));
+	});
+
+	it('keeps oversized inputs verbatim instead of diffing them', () => {
+		// worst case for diffLines is O(N·D); past the size cap the updated content is returned as-is
+		const line = (i: number) => `const value_${i} = compute(${i});`;
+		const old = Array.from({ length: 20_000 }, (_, i) => line(i)).join('\n');
+		const updated = Array.from({ length: 20_000 }, (_, i) => `\t${line(i)}\n`).join('');
+
+		const start = performance.now();
+		expect(minimizeDiff(old, updated)).toBe(updated);
+		expect(performance.now() - start).toBeLessThan(1000);
+	});
+
 	it('keeps updated hunks when non-trailing commas change the meaning', () => {
 		const old = dedent`
 			const values = ['a' + 'b'];

packages/sv/src/cli/tests/snapshots/create-experimental/.env.example

@@ -1,6 +1,8 @@
 # Drizzle
 DATABASE_URL=file:local.db
+
 ORIGIN=""
+
 # Better Auth
 # For production use 32 characters and generated with high entropy
 # https://www.better-auth.com/docs/installation

packages/sv/src/cli/tests/snapshots/create-experimental/src/app.d.ts

@@ -1,4 +1,5 @@
 import type { User, Session } from 'better-auth';
+
 // See https://svelte.dev/docs/kit/types#app.d.ts
 // for information about these interfaces
 declare global {
@@ -9,7 +10,9 @@ declare global {
 			caches: CacheStorage;
 			cf?: IncomingRequestCfProperties
 		}
+
 		interface Locals { user?: User; session?: Session }
+
 		// interface Error {}
 		// interface PageData {}
 		// interface PageState {}

packages/sv/src/cli/tests/snapshots/create-experimental/src/lib/server/db/schema.ts

@@ -5,4 +5,5 @@ export const task = sqliteTable('task', {
 	title: text('title').notNull(),
 	priority: integer('priority').notNull().default(1)
 });
+
 export *  from './auth.schema';

packages/sv/src/cli/tests/snapshots/create-experimental/vite.config.ts

@@ -10,7 +10,6 @@ export default defineConfig({
 				runes: ({ filename }) =>
 					filename.split(/[/\\]/).includes('node_modules') ? undefined : true
 			},
-
 			adapter: adapter(),
 			experimental: { explicitEnvironmentVariables: true },
 			typescript: {

packages/sv/src/cli/tests/snapshots/create-with-all-addons/.env.example

@@ -1,6 +1,8 @@
 # Drizzle
 DATABASE_URL=file:local.db
+
 ORIGIN=""
+
 # Better Auth
 # For production use 32 characters and generated with high entropy
 # https://www.better-auth.com/docs/installation

packages/sv/src/cli/tests/snapshots/create-with-all-addons/src/app.d.ts

@@ -1,9 +1,11 @@
 import type { User, Session } from 'better-auth';
+
 // See https://svelte.dev/docs/kit/types#app.d.ts
 // for information about these interfaces
 declare global {
 	namespace App {
 		interface Locals { user?: User; session?: Session }
+
 		// interface Error {}
 		// interface PageData {}
 		// interface PageState {}

packages/sv/src/cli/tests/snapshots/create-with-all-addons/src/hooks.server.ts

@@ -16,10 +16,13 @@ const handleParaglide: Handle = ({ event, resolve }) => paraglideMiddleware(even
 
 const handleBetterAuth: Handle = async ({ event, resolve }) => {
 	const session = await auth.api.getSession({ headers: event.request.headers });
+
 	if (session) {
 		event.locals.session = session.session;
 		event.locals.user = session.user;
 	}
+
 	return svelteKitHandler({ event, resolve, auth, building });
 };
+
 export const handle: Handle = sequence(handleParaglide, handleBetterAuth);

packages/sv/src/cli/tests/snapshots/create-with-all-addons/src/lib/server/db/schema.ts

@@ -5,4 +5,5 @@ export const task = sqliteTable('task', {
 	title: text('title').notNull(),
 	priority: integer('priority').notNull().default(1)
 });
+
 export *  from './auth.schema';

packages/sv/src/cli/tests/snapshots/create-with-all-addons/src/routes/+layout.svelte

@@ -14,6 +14,7 @@
 </svelte:head>
 
 {@render children()}
+
 <div style="display:none">
 	{#each locales as locale (locale)}
 		<a

packages/sv/src/cli/tests/snapshots/create-with-all-addons/vite.config.ts

@@ -15,7 +15,6 @@ export default defineConfig({
 				runes: ({ filename }) =>
 					filename.split(/[/\\]/).includes('node_modules') ? undefined : true
 			},
-
 			adapter: adapter(),
 			preprocess: [mdsvex({ extensions: ['.svx', '.md'] })],
 			extensions: ['.svelte', '.svx', '.md'],
@@ -44,6 +43,7 @@ export default defineConfig({
 					exclude: ['src/lib/server/**']
 				}
 			},
+
 			{
 				extends: './vite.config.ts',
 				test: {

packages/sv/src/migrate/migrations/app-state/tests/app-state/strings-comments.snapshot.svelte

@@ -6,4 +6,5 @@
 	 * This is a page
 	 */
 </script>
+
 Nice page! <div>{page.url}</div>

packages/sv/src/migrate/migrations/sveltekit-3/tests/environment/dynamic-import-namespace.snapshot.ts

@@ -1,6 +1,7 @@
 export async function requireDynamicImportEnv(name: string): Promise<string> {
 	// @migration-task Declare the imported env variables in src/env.ts manually.
 	const privateEnv = await import('$app/env/private');
+
 	const value = privateEnv[name];
 	if (!value) throw new Error(`${name} must be set`);
 	return value;

packages/sv/src/migrate/migrations/sveltekit-3/tests/svelte-config/eslint.config.snapshot.js

@@ -1,6 +1,7 @@
 import js from '@eslint/js';
 import svelte from 'eslint-plugin-svelte';
 import { defineConfig } from 'eslint/config';
+
 // @migration-task svelteConfig should not be needed anymore, see https://github.com/sveltejs/eslint-plugin-svelte/issues/1550
 import svelteConfig from './svelte.config.js';
 

packages/sv/src/migrate/migrations/sveltekit-3/tests/svelte-config/vite.config.snapshot.ts

@@ -9,7 +9,9 @@ import devtoolsJson from 'vite-plugin-devtools-json';
 
 // derive paths and adapter config from the environment
 const { paths, adapterConfig } = helper(process.env['SOME_ENV_VAR']);
+
 const base = process.env['VITEST'] ? '' : '/some-base'; // empty base while testing
+
 export default defineConfig({
 	plugins: [
 		tailwindcss(),