# Files changed · PR \#23857 · pingdotgg/t3code

[View on GitCafe](https://git.cafe/pingdotgg/t3code/pull/23857/diffs)

Repository: [pingdotgg/t3code](https://git.cafe/pingdotgg/t3code)

Visibility: public

[perf\(web,desktop\): stop re-doing work on every render and unblock the login-shell probe](https://git.cafe/pingdotgg/t3code/pull/23857.md)

Version: 3

Head commit: 8f94364bd90a264a9adb42ca2d1f1166e55da480

Base commit: 2c8bdf6177159d8fcd12a897d7c9311f6eb93237

Comparison base: 2c8bdf6177159d8fcd12a897d7c9311f6eb93237

Showing up to 20 entries from this revision. If the pull request changes, reopen the first page before continuing.

## apps/desktop/src/shell/DesktopShellEnvironment.test.ts

Status: modified; +20; −0

```diff
@@ -170,6 +170,26 @@
     }),
   );
 
+  it.effect("does not leave the login shell's stderr pipe undrained", () =>
+    Effect.gen(function* () {
+      const commands: ChildProcess.Command[] = [];
+
+      yield* runShellEnvironment({
+        env: { SHELL: "/bin/zsh", PATH: "/usr/bin" },
+        platform: "darwin",
+        handler: (command) => {
+          commands.push(command);
+          return envOutput({ PATH: "/opt/homebrew/bin:/usr/bin" });
+        },
+      });
+
+      const command = commands[0];
+      assert.equal(command?._tag, "StandardCommand");
+      // A chatty rc file fills an unread pipe and the shell never exits.
+      assert.equal(command?._tag === "StandardCommand" ? command.options.stderr : "", "ignore");
+    }),
+  );
+
   it.effect("does not mix login-shell locale categories into an inherited locale", () =>
     Effect.gen(function* () {
       const env: NodeJS.ProcessEnv = {
```

## apps/desktop/src/shell/DesktopShellEnvironment.ts

Status: modified; +2; −1

```diff
@@ -254,7 +254,8 @@
           shell: input.shell ?? false,
           stdin: "ignore",
           stdout: "pipe",
+          // Nothing reads stderr; an undrained pipe fills (~64 KB) and blocks the shell.
+          stderr: "ignore",
-          stderr: "pipe",
           killSignal: "SIGTERM",
           forceKillAfter: PROCESS_TERMINATE_GRACE,
         }),
```

## apps/web/src/components/ChatMarkdown.tsx

Status: modified; +3; −1

```diff
@@ -1582,6 +1582,8 @@
     props.isStreaming === true &&
     extraRemarkPlugins.length === 0 &&
     /(?:^|\n) {0,3}(?:`{3}|~{3})/.test(text);
+  // The plugin's prefix cache lives in its closure, so it must outlive renders.
+  const [incrementalPlugin] = useState(createIncrementalMarkdownPlugin);
   const Root = inline ? "span" : "div";
   const bindMarkdownRef = (node: HTMLElement | null) => {
     markdownRef.current = node;
@@ -1589,7 +1591,7 @@
   const remarkPlugins = [
     ...(lineBreaks ? CHAT_MARKDOWN_REMARK_PLUGINS_WITH_BREAKS : CHAT_MARKDOWN_REMARK_PLUGINS),
     ...extraRemarkPlugins,
-    ...(incrementalParsing ? [createIncrementalMarkdownPlugin()] : []),
+    ...(incrementalParsing ? [incrementalPlugin] : []),
   ];
   if (componentState.mathEnabled)
     remarkPlugins.unshift([remarkMath, { singleDollarTextMath: true }]);
```

## apps/web/src/components/DiffPanel.tsx

Status: modified; +22; −2

```diff
@@ -43,6 +43,7 @@
   getDiffCollapseIconClassName,
   getDiffLineStat,
   getRenderablePatch,
+  type RenderablePatch,
   resolveDiffThemeName,
   resolveFileDiffPath,
 } from "../lib/diffRendering";
@@ -98,6 +99,25 @@
 type DiffThemeType = "light" | "dark";
 const AUTOMATIC_BASE_REF = "__automatic_base_ref__";
 const DIFF_FILE_TREE_STORAGE_KEY = "t3code.diffFileTreeOpen";
+// The patch is a string, so it cannot key a WeakMap. One entry per option set, compared by
+// value, keeps unrelated renders (typing in the base-ref box, toggling wrap) from re-parsing
+// it. Parsing yields fresh file objects, which would also defeat fileEntryCache below.
+const renderablePatchCache = new Map<string, { patch: string; value: RenderablePatch | null }>();
+
+function getCachedRenderablePatch(
+  patch: string | undefined,
+  theme: string,
+  options: { compactPartialHunkOffsets: boolean; ignoreWhitespace?: boolean },
+) {
+  const cacheScope = `diff-panel:${theme}`;
+  const key = `${cacheScope}|${options.compactPartialHunkOffsets}|${options.ignoreWhitespace === true}`;
+  const cached = renderablePatchCache.get(key);
+  if (cached && cached.patch === patch) return cached.value;
+  const value = getRenderablePatch(patch, cacheScope, options);
+  if (patch) renderablePatchCache.set(key, { patch, value });
+  return value;
+}
+
 const fileEntryCache = new WeakMap<
   FileDiffMetadata,
   { fileDiff: FileDiffMetadata; fileKey: string; fileVersion: number }
@@ -358,9 +378,9 @@
     !selectedTurn && selectedGitSource?.truncated && selectedGitSource.files
       ? selectedGitSource
       : null;
-  const renderablePatch = getRenderablePatch(
+  const renderablePatch = getCachedRenderablePatch(
     lazySource ? undefined : selectedPatch,
+    resolvedTheme,
-    `diff-panel:${resolvedTheme}`,
     { compactPartialHunkOffsets: selectedRunId === null },
   );
   const fileStats = new Map(lazySource?.files?.map((file) => [file.path, file]));
```

## apps/web/src/hooks/useLocalStorage.ts

Status: modified; +14; −2

```diff
@@ -40,9 +40,21 @@
   }
 };
 
+// Building the JSON codec walks the schema, and it ran on every render of every consumer.
+const jsonCodecs = new WeakMap<Schema.Codec<any, any>, Schema.Codec<any, string>>();
+
+const jsonCodec = <T, E>(schema: Schema.Codec<T, E>) => {
+  let codec = jsonCodecs.get(schema);
+  if (codec === undefined) {
+    codec = Schema.fromJsonString(schema);
+    jsonCodecs.set(schema, codec);
+  }
+  return codec as Schema.Codec<T, string>;
+};
+
 const decode = <T, E>(key: string, schema: Schema.Codec<T, E>, value: string) => {
   try {
-    return Schema.decodeSync(Schema.fromJsonString(schema))(value);
+    return Schema.decodeSync(jsonCodec(schema))(value);
   } catch (cause) {
     throw new LocalStorageOperationError({ operation: "decode", storageKey: key, cause });
   }
@@ -50,7 +62,7 @@
 
 const encode = <T, E>(key: string, schema: Schema.Codec<T, E>, value: T) => {
   try {
-    return Schema.encodeSync(Schema.fromJsonString(schema))(value);
+    return Schema.encodeSync(jsonCodec(schema))(value);
   } catch (cause) {
     throw new LocalStorageOperationError({ operation: "encode", storageKey: key, cause });
   }
```

## apps/web/src/markdown-incremental.test.tsx

Status: modified; +28; −0

````diff
@@ -132,4 +132,32 @@
       }
     }
   });
+
+  it("parses a different message in full after the plugin served another one", () => {
+    const incremental = createIncrementalMarkdownPlugin();
+    const first = prefix + "first message tail";
+    const second = "# Other\n\n```ts\nconst other = 1;\n```\n\nsecond message tail";
+    // The plugin keeps the first renderer's parser, so one array must observe every render.
+    const parsedSources: string[] = [];
+    render(first, incremental, parsedSources);
+    render(first + " more", incremental, parsedSources);
+    parsedSources.length = 0;
+    expect(render(second, incremental, parsedSources)).toEqual(render(second));
+    expect(parsedSources).toContain(second);
+  });
+
+  it("parses less text with one plugin instance than with a fresh instance per render", () => {
+    const source = `\`\`\`ts\n${"const value = 1;\n".repeat(200)}\`\`\`\n\nstreaming tail`;
+    const documents = [source, source + "a", source + "ab"];
+    const parsedLength = (pluginFor: () => Plugin<[], Root>) => {
+      // A plugin keeps its first renderer's parser, so one array observes every render.
+      const sources: string[] = [];
+      for (const text of documents) render(text, pluginFor(), sources);
+      return sources.reduce((total, part) => total + part.length, 0);
+    };
+    const persistent = createIncrementalMarkdownPlugin();
+    const shared = parsedLength(() => persistent);
+    const fresh = parsedLength(() => createIncrementalMarkdownPlugin());
+    expect(shared).toBeLessThan(fresh);
+  });
 });
````

## apps/web/src/terminal/links.bench.ts

Status: added; +25; −0

```diff
@@ -1,0 +1,25 @@
+import { describe, test } from "vite-plus/test";
+
+import { extractTerminalLinks } from "../terminal-links";
+
+// Hover detection runs this over a whole wrapped logical line on every frame,
+// so separator-free output must stay linear in length.
+const dense = (length: number) => "a1B2c3".repeat(Math.ceil(length / 6)).slice(0, length);
+const spaced = (length: number) => "word ".repeat(Math.ceil(length / 5)).slice(0, length);
+
+for (const length of [2_000, 10_000]) {
+  describe(`extractTerminalLinks over ${length} chars`, () => {
+    const denseText = dense(length);
+    const spacedText = spaced(length);
+    test("dense (no spaces)", async ({ bench }) => {
+      await bench("dense", () => {
+        extractTerminalLinks(denseText);
+      }).run();
+    });
+    test("spaced", async ({ bench }) => {
+      await bench("spaced", () => {
+        extractTerminalLinks(spacedText);
+      }).run();
+    });
+  });
+}
```