fix(desktop): symlinked desktop and client settings stay linked

apps/desktop/src/settings/DesktopAppSettings.test.ts

@@ -357,6 +357,34 @@ describe("DesktopSettings", () => {
     ),
   );
 
+  it.effect("saves through a symlinked settings file without replacing the link", () =>
+    withSettings(
+      Effect.gen(function* () {
+        const environment = yield* DesktopEnvironment.DesktopEnvironment;
+        const fileSystem = yield* FileSystem.FileSystem;
+        const settings = yield* DesktopAppSettings.DesktopAppSettings;
+        const dotfiles = yield* fileSystem.makeTempDirectoryScoped({
+          prefix: "t3-desktop-settings-dotfiles-",
+        });
+        const linkedSettingsPath = `${dotfiles}/desktop-settings.json`;
+        yield* fileSystem.writeFileString(linkedSettingsPath, "{}\n");
+        yield* fileSystem.makeDirectory(environment.stateDir, { recursive: true });
+        yield* fileSystem.symlink(linkedSettingsPath, environment.desktopSettingsPath);
+
+        yield* settings.setServerExposureMode("network-accessible");
+
+        assert.equal(
+          yield* fileSystem.readLink(environment.desktopSettingsPath),
+          linkedSettingsPath,
+        );
+        const persisted = yield* decodeDesktopSettingsPatch(
+          yield* fileSystem.readFileString(linkedSettingsPath),
+        );
+        assert.equal(persisted.serverExposureMode, "network-accessible");
+      }),
+    ),
+  );
+
   it.effect("migrates legacy implicit update channels to the runtime default", () =>
     withSettings(
       Effect.gen(function* () {

apps/desktop/src/settings/DesktopAppSettings.ts

@@ -5,6 +5,7 @@ import {
   type DesktopUpdateChannel,
 } from "@t3tools/contracts";
 import { fromLenientJson } from "@t3tools/shared/schemaJson";
+import { resolveSymlinkTarget } from "@t3tools/shared/symlink";
 import * as Context from "effect/Context";
 import * as Crypto from "effect/Crypto";
 import * as Effect from "effect/Effect";
@@ -421,8 +422,12 @@ const writeSettings = Effect.fn("desktop.settings.writeSettings")(function* (inp
   readonly defaultSettings: DesktopSettings;
   readonly suffix: string;
 }): Effect.fn.Return<void, DesktopSettingsWriteError> {
-  const directory = input.path.dirname(input.settingsPath);
-  const tempPath = `${input.settingsPath}.${process.pid}.${input.suffix}.tmp`;
+  const targetPath = yield* resolveSymlinkTarget(input.settingsPath).pipe(
+    Effect.provideService(FileSystem.FileSystem, input.fileSystem),
+    Effect.provideService(Path.Path, input.path),
+  );
+  const directory = input.path.dirname(targetPath);
+  const tempPath = `${targetPath}.${process.pid}.${input.suffix}.tmp`;
   const encoded = yield* encodeDesktopSettingsJson(
     toDesktopSettingsDocument(input.settings, input.defaultSettings),
   ).pipe(
@@ -455,7 +460,7 @@ const writeSettings = Effect.fn("desktop.settings.writeSettings")(function* (inp
         }),
     ),
   );
-  yield* input.fileSystem.rename(tempPath, input.settingsPath).pipe(
+  yield* input.fileSystem.rename(tempPath, targetPath).pipe(
     Effect.mapError(
       (cause) =>
         new DesktopSettingsWriteError({

apps/desktop/src/settings/DesktopClientSettings.test.ts

@@ -149,6 +149,34 @@ describe("DesktopClientSettings", () => {
     ),
   );
 
+  it.effect("saves through a symlinked client settings file without replacing the link", () =>
+    withClientSettings(
+      Effect.gen(function* () {
+        const environment = yield* DesktopEnvironment.DesktopEnvironment;
+        const fileSystem = yield* FileSystem.FileSystem;
+        const settings = yield* DesktopClientSettings.DesktopClientSettings;
+        const dotfiles = yield* fileSystem.makeTempDirectoryScoped({
+          prefix: "t3-desktop-client-settings-dotfiles-",
+        });
+        const linkedSettingsPath = `${dotfiles}/client-settings.json`;
+        yield* fileSystem.writeFileString(linkedSettingsPath, "{}\n");
+        yield* fileSystem.makeDirectory(environment.stateDir, { recursive: true });
+        yield* fileSystem.symlink(linkedSettingsPath, environment.clientSettingsPath);
+
+        yield* settings.set(clientSettings);
+
+        assert.equal(
+          yield* fileSystem.readLink(environment.clientSettingsPath),
+          linkedSettingsPath,
+        );
+        assert.deepEqual(
+          yield* decodeClientSettingsJson(yield* fileSystem.readFileString(linkedSettingsPath)),
+          clientSettings,
+        );
+      }),
+    ),
+  );
+
   for (const failure of [
     { label: "permission", reason: "PermissionDenied" },
     { label: "I/O", reason: "Unknown" },

apps/desktop/src/settings/DesktopClientSettings.ts

@@ -1,5 +1,6 @@
 import { ClientSettingsSchema, type ClientSettings } from "@t3tools/contracts";
 import { fromLenientJson } from "@t3tools/shared/schemaJson";
+import { resolveSymlinkTarget } from "@t3tools/shared/symlink";
 import * as Context from "effect/Context";
 import * as Crypto from "effect/Crypto";
 import * as Effect from "effect/Effect";
@@ -126,8 +127,12 @@ const writeClientSettings = Effect.fnUntraced(function* (input: {
   readonly settings: ClientSettings;
   readonly suffix: string;
 }): Effect.fn.Return<void, DesktopClientSettingsWriteError> {
-  const directory = input.path.dirname(input.settingsPath);
-  const tempPath = `${input.settingsPath}.${process.pid}.${input.suffix}.tmp`;
+  const targetPath = yield* resolveSymlinkTarget(input.settingsPath).pipe(
+    Effect.provideService(FileSystem.FileSystem, input.fileSystem),
+    Effect.provideService(Path.Path, input.path),
+  );
+  const directory = input.path.dirname(targetPath);
+  const tempPath = `${targetPath}.${process.pid}.${input.suffix}.tmp`;
   const encoded = yield* encodeClientSettingsJson(input.settings).pipe(
     Effect.mapError(
       (cause) =>
@@ -158,7 +163,7 @@ const writeClientSettings = Effect.fnUntraced(function* (input: {
         }),
     ),
   );
-  yield* input.fileSystem.rename(tempPath, input.settingsPath).pipe(
+  yield* input.fileSystem.rename(tempPath, targetPath).pipe(
     Effect.mapError(
       (cause) =>
         new DesktopClientSettingsWriteError({

apps/server/src/atomicWrite.ts

@@ -1,27 +1,7 @@
 import * as Effect from "effect/Effect";
 import * as FileSystem from "effect/FileSystem";
 import * as Path from "effect/Path";
-
-const MAX_SYMLINK_HOPS = 40;
-
-/**
- * Follows a chain of symlinks to the file it finally names, which may not exist
- * yet. Any path that is not a symlink resolves to itself.
- */
-export const resolveSymlinkTarget = (filePath: string) =>
-  Effect.gen(function* () {
-    const fs = yield* FileSystem.FileSystem;
-    const path = yield* Path.Path;
-    let current = path.resolve(filePath);
-    for (let hop = 0; hop < MAX_SYMLINK_HOPS; hop++) {
-      const link = yield* fs.readLink(current).pipe(Effect.option);
-      if (link._tag === "None") {
-        return current;
-      }
-      current = path.resolve(path.dirname(current), link.value);
-    }
-    return current;
-  });
+import { resolveSymlinkTarget } from "@t3tools/shared/symlink";
 
 /**
  * Replaces a file's contents via a sibling temp file and rename. A symlinked

apps/server/src/serverSettings.ts

@@ -51,7 +51,8 @@ import * as Semaphore from "effect/Semaphore";
 import * as Scope from "effect/Scope";
 import * as Stream from "effect/Stream";
 import * as SqlClient from "effect/unstable/sql/SqlClient";
-import { resolveSymlinkTarget, writeFileStringAtomically } from "./atomicWrite.ts";
+import { writeFileStringAtomically } from "./atomicWrite.ts";
+import { resolveSymlinkTarget } from "@t3tools/shared/symlink";
 import * as ServerConfig from "./config.ts";
 import { type DeepPartial, deepMerge } from "@t3tools/shared/Struct";
 import { fromJsonStringPretty, fromLenientJson } from "@t3tools/shared/schemaJson";

docs/fork/0027-symlinked-settings-stay-linked.md

@@ -1,6 +1,6 @@
 # 0027: Symlinked settings stay linked
 
-- PR: [TrogonStack/t3code#73](https://github.com/TrogonStack/t3code/pull/73)
+- PRs: [TrogonStack/t3code#73](https://github.com/TrogonStack/t3code/pull/73), [TrogonStack/t3code#74](https://github.com/TrogonStack/t3code/pull/74)
 - Status: active
 
 ## What you can do now

docs/fork/README.md

@@ -44,4 +44,4 @@ Each entry uses these sections:
 - **0025** [A test run leaves no processes behind](./0025-a-test-run-leaves-no-processes-behind.md)
   active, [#57](https://github.com/TrogonStack/t3code/pull/57)
 - **0027** [Symlinked settings stay linked](./0027-symlinked-settings-stay-linked.md)
-  active, [#73](https://github.com/TrogonStack/t3code/pull/73)
+  active, [#73](https://github.com/TrogonStack/t3code/pull/73), [#74](https://github.com/TrogonStack/t3code/pull/74)

packages/shared/package.json

@@ -195,6 +195,10 @@
       "types": "./src/connectAuth.ts",
       "import": "./src/connectAuth.ts"
     },
+    "./symlink": {
+      "types": "./src/symlink.ts",
+      "import": "./src/symlink.ts"
+    },
     "./path": {
       "types": "./src/path.ts",
       "import": "./src/path.ts"

packages/shared/src/symlink.ts

@@ -0,0 +1,25 @@
+import * as Effect from "effect/Effect";
+import * as FileSystem from "effect/FileSystem";
+import * as Path from "effect/Path";
+
+const MAX_SYMLINK_HOPS = 40;
+
+/**
+ * Follows a chain of symlinks to the file it finally names, which may not exist
+ * yet. Any path that is not a symlink resolves to itself. Atomic writers rename
+ * onto this path so a linked file keeps its link.
+ */
+export const resolveSymlinkTarget = (filePath: string) =>
+  Effect.gen(function* () {
+    const fs = yield* FileSystem.FileSystem;
+    const path = yield* Path.Path;
+    let current = path.resolve(filePath);
+    for (let hop = 0; hop < MAX_SYMLINK_HOPS; hop++) {
+      const link = yield* fs.readLink(current).pipe(Effect.option);
+      if (link._tag === "None") {
+        return current;
+      }
+      current = path.resolve(path.dirname(current), link.value);
+    }
+    return current;
+  });