refactor(config+core): drop ConfigPaths.readFile, add AppFileSystem.readFileStringSafe, flatten TuiConfig.loadState (#25602)

packages/core/src/filesystem.ts

@@ -24,6 +24,7 @@ export namespace AppFileSystem {
     readonly isDir: (path: string) => Effect.Effect<boolean>
     readonly isFile: (path: string) => Effect.Effect<boolean>
     readonly existsSafe: (path: string) => Effect.Effect<boolean>
+    readonly readFileStringSafe: (path: string) => Effect.Effect<string | undefined, Error>
     readonly readJson: (path: string) => Effect.Effect<unknown, Error>
     readonly writeJson: (path: string, data: unknown, mode?: number) => Effect.Effect<void, Error>
     readonly ensureDir: (path: string) => Effect.Effect<void, Error>
@@ -47,6 +48,12 @@ export namespace AppFileSystem {
         return yield* fs.exists(path).pipe(Effect.orElseSucceed(() => false))
       })
 
+      const readFileStringSafe = Effect.fn("FileSystem.readFileStringSafe")(function* (path: string) {
+        return yield* fs
+          .readFileString(path)
+          .pipe(Effect.catchReason("PlatformError", "NotFound", () => Effect.succeed(undefined)))
+      })
+
       const isDir = Effect.fn("FileSystem.isDir")(function* (path: string) {
         const info = yield* fs.stat(path).pipe(Effect.catch(() => Effect.void))
         return info?.type === "Directory"
@@ -163,6 +170,7 @@ export namespace AppFileSystem {
       return Service.of({
         ...fs,
         existsSafe,
+        readFileStringSafe,
         isDir,
         isFile,
         readDirectoryEntries,

packages/core/test/filesystem/filesystem.test.ts

@@ -65,6 +65,34 @@ describe("AppFileSystem", () => {
     )
   })
 
+  describe("readFileStringSafe", () => {
+    it(
+      "returns file contents when file exists",
+      Effect.gen(function* () {
+        const fs = yield* AppFileSystem.Service
+        const filesys = yield* FileSystem.FileSystem
+        const tmp = yield* filesys.makeTempDirectoryScoped()
+        const file = path.join(tmp, "exists.txt")
+        yield* filesys.writeFileString(file, "hello")
+
+        const result = yield* fs.readFileStringSafe(file)
+        expect(result).toBe("hello")
+      }),
+    )
+
+    it(
+      "returns undefined for missing file (NotFound)",
+      Effect.gen(function* () {
+        const fs = yield* AppFileSystem.Service
+        const filesys = yield* FileSystem.FileSystem
+        const tmp = yield* filesys.makeTempDirectoryScoped()
+
+        const result = yield* fs.readFileStringSafe(path.join(tmp, "does-not-exist.txt"))
+        expect(result).toBeUndefined()
+      }),
+    )
+  })
+
   describe("readJson / writeJson", () => {
     it(
       "round-trips JSON data",