feat: port noise-filtered diff parsing engine
Add src/diff.ts: a reusable unified-diff engine that parses diffs into per-file +/− stats and filters noise (lockfiles, minified/generated assets, source maps, snapshots, build output, node_modules/vendor, binary/media) so review prompts feed only clean, review-relevant changes. Exports DiffSummary/FileDiff shapes, EXCLUDED_PATTERNS, isExcluded, parseDiff, plus filterNoise and configurable extra-pattern/ignore-path overrides. Malformed diff chunks are skipped without crashing, and excluded files are never double-counted into totals. Add tests/diff.test.ts covering the included/excluded split, per-file +/− counts, totals excluding noise, malformed-chunk guard, and the noise-filter override rules.
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tests/diff.test.ts
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tests/diff.test.ts
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/**
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* Tests for the noise-filtered diff engine (src/diff.ts).
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* Covers: per-file +/− parsing, excluded-file split, totals excluding noise,
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* malformed-chunk guard, isExcluded reasons, and configurable overrides.
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*/
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import { describe, test, expect } from "bun:test";
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import {
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parseDiff,
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filterNoise,
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isExcluded,
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compileIgnorePatterns,
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EXCLUDED_PATTERNS,
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} from "../src/diff";
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/** A synthetic unified diff mixing code, a lockfile, a minified file, and a binary. */
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const SYNTH_DIFF = [
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"diff --git a/src/index.ts b/src/index.ts",
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"index 111..222 100644",
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"--- a/src/index.ts",
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"+++ b/src/index.ts",
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"@@ -1,2 +1,4 @@",
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' import { foo } from "./foo";',
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"+export const baz = 1;",
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"+export const qux = 2;",
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"-foo();",
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"+bar();",
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"",
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"diff --git a/package-lock.json b/package-lock.json",
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"index 000..111 100644",
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"--- a/package-lock.json",
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"+++ b/package-lock.json",
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"@@ -0,0 +1,3 @@",
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"+{",
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'+ "name": "x"',
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"+}",
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"",
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"diff --git a/dist/foo.min.js b/dist/foo.min.js",
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"index 111..222 100644",
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"--- a/dist/foo.min.js",
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"+++ b/dist/foo.min.js",
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"@@ -1 +1 @@",
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"-var a=1;",
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"+var a=2;",
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"",
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"diff --git a/assets/logo.png b/assets/logo.png",
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"index 111..222 100644",
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"Binary files differ",
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].join("\n");
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describe("parseDiff", () => {
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test("splits included vs excluded files and totals only included", () => {
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const summary = parseDiff(SYNTH_DIFF);
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// Included: only src/index.ts (code). Lockfile, minified, binary excluded.
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expect(summary.files).toHaveLength(1);
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expect(summary.files[0]).toEqual({
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path: "src/index.ts",
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linesAdded: 3,
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linesRemoved: 1,
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ext: "ts",
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});
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expect(summary.excluded).toHaveLength(3);
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const byPath = new Map(
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summary.excluded.map((f) => [f.path, f]),
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);
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expect(byPath.get("package-lock.json")).toMatchObject({
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linesAdded: 3,
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linesRemoved: 0,
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reason: "lockfile",
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});
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expect(byPath.get("dist/foo.min.js")).toMatchObject({
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linesAdded: 1,
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linesRemoved: 1,
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reason: "minified asset",
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});
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expect(byPath.get("assets/logo.png")).toMatchObject({
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linesAdded: 0,
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linesRemoved: 0,
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reason: "binary/media asset",
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});
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// Totals exclude the noise files.
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expect(summary.totalAdded).toBe(3);
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expect(summary.totalRemoved).toBe(1);
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});
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test("returns empty summary for an empty diff", () => {
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const summary = parseDiff("");
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expect(summary.files).toHaveLength(0);
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expect(summary.excluded).toHaveLength(0);
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expect(summary.totalAdded).toBe(0);
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expect(summary.totalRemoved).toBe(0);
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});
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test("skips malformed chunks without a/… b/ header without crashing", () => {
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const malformed =
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"diff --git weird-line\nindex 111..222\n--- a/x\n+++ b/x\n+x\n" +
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"\n" +
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"diff --git a/src/ok.ts b/src/ok.ts\n--- a/src/ok.ts\n+++ b/src/ok.ts\n+ok\n";
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const summary = parseDiff(malformed);
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// Only the well-formed chunk is counted.
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expect(summary.files).toHaveLength(1);
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expect(summary.files[0].path).toBe("src/ok.ts");
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expect(summary.totalAdded).toBe(1);
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});
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test("does not count +++/--- header lines as additions/removals", () => {
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const diff = [
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"diff --git a/src/a.ts b/src/a.ts",
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"--- a/src/a.ts",
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"+++ b/src/a.ts",
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"@@ -0,0 +1,2 @@",
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"+one",
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"+two",
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].join("\n");
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const summary = parseDiff(diff);
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expect(summary.files[0].linesAdded).toBe(2);
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expect(summary.files[0].linesRemoved).toBe(0);
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});
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});
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describe("isExcluded", () => {
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test("returns the right reason per pattern", () => {
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expect(isExcluded("package-lock.json")).toBe("lockfile");
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expect(isExcluded("yarn.lock")).toBe("lockfile");
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expect(isExcluded("src/app.min.js")).toBe("minified asset");
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expect(isExcluded("src/styles.min.css")).toBe("minified asset");
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expect(isExcluded("build/out.js")).toBe("build output");
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expect(isExcluded("node_modules/foo/index.js")).toBe("dependency");
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expect(isExcluded("vendor/lib.bundle.js")).toBe("vendored dependency");
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expect(isExcluded("assets/icon.svg")).toBe("binary/media asset");
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expect(isExcluded("src/api.generated.ts")).toBe("generated file");
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expect(isExcluded("test/__snapshots__/x.snap")).toBe("snapshot");
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expect(isExcluded("dist/x.js.map")).toBe("source map");
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});
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test("returns undefined for review-relevant files", () => {
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expect(isExcluded("src/foo.ts")).toBeUndefined();
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expect(isExcluded("src/index.ts")).toBeUndefined();
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});
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test("merges caller-supplied extra patterns", () => {
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expect(isExcluded("src/data.foo", [/\.foo$/])).toBe("extra ignore pattern");
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expect(isExcluded("src/data.foo")).toBeUndefined();
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});
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test("EXCLUDED_PATTERNS covers lockfiles, min, generated, snap, map, build, vendor, binaries", () => {
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for (const pat of [
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"package-lock.json",
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"src/app.min.js",
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"src/thing.generated.ts",
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"x.snap",
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"x.js.map",
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"dist/bundle.js",
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"node_modules/a/b.js",
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"vendor/x",
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"a.png",
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"f.woff2",
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]) {
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const hit = EXCLUDED_PATTERNS.some((r) => r.pattern.test(pat));
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expect(hit, `${pat} should be covered by a default rule`).toBe(true);
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}
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});
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});
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describe("filterNoise", () => {
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test("re-emits only included-file chunks", () => {
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const filtered = filterNoise(SYNTH_DIFF);
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expect(filtered).toContain("diff --git a/src/index.ts");
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expect(filtered).not.toContain("package-lock.json");
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expect(filtered).not.toContain("foo.min.js");
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expect(filtered).not.toContain("logo.png");
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});
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test("returns empty when every file is noise", () => {
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const onlyNoise = [
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"diff --git a/package-lock.json b/package-lock.json",
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"--- a/package-lock.json",
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"+++ b/package-lock.json",
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"+x",
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].join("\n");
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expect(filterNoise(onlyNoise)).toBe("");
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});
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});
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describe("configurable noise rules", () => {
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test("extraPatterns excludes a matching file from the review diff", () => {
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const diff = [
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"diff --git a/src/foo.ts b/src/foo.ts",
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"--- a/src/foo.ts",
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"+++ b/src/foo.ts",
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"+keep",
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"diff --git a/src/data.foo b/src/data.foo",
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"--- a/src/data.foo",
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"+++ b/src/data.foo",
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"+drop",
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].join("\n");
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const opts = { extraPatterns: compileIgnorePatterns(["\\.foo$"]) };
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const summary = parseDiff(diff, opts);
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expect(summary.files.map((f) => f.path)).toEqual(["src/foo.ts"]);
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expect(summary.excluded.map((f) => [f.path, f.reason])).toEqual([
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["src/data.foo", "extra ignore pattern"],
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]);
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expect(filterNoise(diff, opts)).not.toContain("data.foo");
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});
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test("ignorePaths keeps an excluded-by-default file in scope", () => {
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const diff = [
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"diff --git a/package-lock.json b/package-lock.json",
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"--- a/package-lock.json",
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"+++ b/package-lock.json",
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"+a",
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"+b",
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"+c",
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].join("\n");
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const opts = { ignorePaths: ["package-lock.json"] };
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const summary = parseDiff(diff, opts);
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expect(summary.files).toHaveLength(1);
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expect(summary.files[0].path).toBe("package-lock.json");
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expect(summary.excluded).toHaveLength(0);
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expect(summary.totalAdded).toBe(3);
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expect(filterNoise(diff, opts)).toContain("package-lock.json");
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});
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test("default behavior unchanged when overrides are unset", () => {
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const summary = parseDiff(SYNTH_DIFF);
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expect(summary.files[0].path).toBe("src/index.ts");
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expect(summary.totalAdded).toBe(3);
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});
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test("compileIgnorePatterns skips invalid regexes", () => {
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const compiled = compileIgnorePatterns(["\\.foo$", "(", "ok$"]);
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expect(compiled.length).toBe(2);
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});
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});
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