perf(tui): skip redundant dependency installs

nanobot/cli/tui_launcher.py

@@ -67,6 +67,8 @@ _TUI_RELEASE_LIMITS = {
 _TUI_DETACH_EXIT_CODE = 90
 _GATEWAY_READY_TIMEOUT_S = 20.0
 _GATEWAY_READY_POLL_S = 0.1
+_TUI_DEPENDENCY_METADATA = ("package.json", "bun.lock")
+_TUI_DEPENDENCY_CACHE = ".nanobot-install.sha256"
 
 
 @dataclass(frozen=True)
@@ -224,6 +226,21 @@ def _tui_source_dir(project_root: Path) -> Path | None:
 
 def _resolve_source_tui_command(source_dir: Path, bun: str) -> list[str]:
     dependency = source_dir / "node_modules" / "@opentui" / "core"
+    cache = source_dir / "node_modules" / _TUI_DEPENDENCY_CACHE
+    fingerprint = _tui_dependency_fingerprint(source_dir)
+    if dependency.is_dir() and fingerprint is not None:
+        try:
+            if cache.read_text(encoding="ascii") == f"{fingerprint}\n":
+                return _source_tui_command(source_dir, bun)
+        except (OSError, UnicodeError):
+            pass
+
+    try:
+        cache.unlink(missing_ok=True)
+    except OSError as exc:
+        raise TuiUnavailableError(
+            f"could not prepare the TUI dependency install: {exc}"
+        ) from exc
     try:
         install = subprocess.run(
             [bun, "install", "--frozen-lockfile"],
@@ -238,6 +255,37 @@ def _resolve_source_tui_command(source_dir: Path, bun: str) -> list[str]:
         detail = (install.stderr or install.stdout).strip().splitlines()
         suffix = f": {detail[-1]}" if detail else ""
         raise TuiUnavailableError(f"could not install TUI dependencies{suffix}")
+
+    current_fingerprint = _tui_dependency_fingerprint(source_dir)
+    if fingerprint is not None and current_fingerprint == fingerprint:
+        pending = cache.with_name(f"{cache.name}.tmp-{os.getpid()}")
+        try:
+            pending.write_text(f"{fingerprint}\n", encoding="ascii")
+            pending.replace(cache)
+        except OSError:
+            try:
+                pending.unlink(missing_ok=True)
+            except OSError:
+                pass
+
+    return _source_tui_command(source_dir, bun)
+
+
+def _tui_dependency_fingerprint(source_dir: Path) -> str | None:
+    digest = hashlib.sha256()
+    try:
+        for name in _TUI_DEPENDENCY_METADATA:
+            content = (source_dir / name).read_bytes()
+            digest.update(name.encode())
+            digest.update(b"\0")
+            digest.update(len(content).to_bytes(8, "big"))
+            digest.update(content)
+    except OSError:
+        return None
+    return digest.hexdigest()
+
+
+def _source_tui_command(source_dir: Path, bun: str) -> list[str]:
     executable = named_executable(
         bun,
         name="nanobot-tui",

tests/cli/test_tui_launcher.py

@@ -51,6 +51,14 @@ def _release_archive(
     return payload, checksum
 
 
+def _tui_source(tmp_path: Path) -> Path:
+    source_dir = tmp_path / "tui"
+    source_dir.mkdir()
+    (source_dir / "package.json").write_text('{"dependencies": {}}\n', encoding="utf-8")
+    (source_dir / "bun.lock").write_text('lockfileVersion = 1\n', encoding="utf-8")
+    return source_dir
+
+
 @pytest.mark.parametrize(
     ("session_id", "expected"),
     [
@@ -525,18 +533,18 @@ def test_classic_options_require_an_explicit_classic_prompt(
         )
 
 
-def test_source_checkout_refreshes_locked_tui_dependencies(
+def test_source_checkout_installs_missing_locked_tui_dependencies(
     monkeypatch: pytest.MonkeyPatch,
     tmp_path: Path,
 ) -> None:
-    source_dir = tmp_path / "tui"
-    source_dir.mkdir()
-    (source_dir / "node_modules" / "@opentui" / "core").mkdir(parents=True)
+    source_dir = _tui_source(tmp_path)
+    dependency = source_dir / "node_modules" / "@opentui" / "core"
     bun = str(tmp_path / "bun")
 
     def install(command: list[str], **kwargs: object) -> subprocess.CompletedProcess[str]:
         assert command == [bun, "install", "--frozen-lockfile"]
         assert kwargs["cwd"] == source_dir
+        dependency.mkdir(parents=True)
         return subprocess.CompletedProcess(command, 0, "", "")
 
     monkeypatch.setattr("nanobot.cli.tui_launcher.subprocess.run", install)
@@ -551,6 +559,82 @@ def test_source_checkout_refreshes_locked_tui_dependencies(
     ]
 
 
+def test_source_checkout_skips_install_when_locked_dependencies_are_current(
+    monkeypatch: pytest.MonkeyPatch,
+    tmp_path: Path,
+) -> None:
+    source_dir = _tui_source(tmp_path)
+    dependency = source_dir / "node_modules" / "@opentui" / "core"
+    installs: list[list[str]] = []
+
+    def install(command: list[str], **_kwargs: object) -> subprocess.CompletedProcess[str]:
+        installs.append(command)
+        dependency.mkdir(parents=True)
+        return subprocess.CompletedProcess(command, 0, "", "")
+
+    monkeypatch.setattr("nanobot.cli.tui_launcher.subprocess.run", install)
+
+    _resolve_source_tui_command(source_dir, "bun")
+    _resolve_source_tui_command(source_dir, "bun")
+
+    assert installs == [["bun", "install", "--frozen-lockfile"]]
+
+
+@pytest.mark.parametrize("metadata_name", ["package.json", "bun.lock"])
+def test_source_checkout_refreshes_dependencies_when_metadata_changes(
+    monkeypatch: pytest.MonkeyPatch,
+    tmp_path: Path,
+    metadata_name: str,
+) -> None:
+    source_dir = _tui_source(tmp_path)
+    dependency = source_dir / "node_modules" / "@opentui" / "core"
+    installs: list[list[str]] = []
+
+    def install(command: list[str], **_kwargs: object) -> subprocess.CompletedProcess[str]:
+        installs.append(command)
+        dependency.mkdir(parents=True, exist_ok=True)
+        return subprocess.CompletedProcess(command, 0, "", "")
+
+    monkeypatch.setattr("nanobot.cli.tui_launcher.subprocess.run", install)
+
+    _resolve_source_tui_command(source_dir, "bun")
+    with (source_dir / metadata_name).open("a", encoding="utf-8") as metadata:
+        metadata.write("changed\n")
+    _resolve_source_tui_command(source_dir, "bun")
+
+    assert installs == [
+        ["bun", "install", "--frozen-lockfile"],
+        ["bun", "install", "--frozen-lockfile"],
+    ]
+
+
+def test_failed_source_dependency_install_does_not_leave_a_valid_cache(
+    monkeypatch: pytest.MonkeyPatch,
+    tmp_path: Path,
+) -> None:
+    source_dir = _tui_source(tmp_path)
+    dependency = source_dir / "node_modules" / "@opentui" / "core"
+    outcomes = iter((0, 1, 0))
+    installs = 0
+
+    def install(command: list[str], **_kwargs: object) -> subprocess.CompletedProcess[str]:
+        nonlocal installs
+        installs += 1
+        dependency.mkdir(parents=True, exist_ok=True)
+        returncode = next(outcomes)
+        return subprocess.CompletedProcess(command, returncode, "", "partial install")
+
+    monkeypatch.setattr("nanobot.cli.tui_launcher.subprocess.run", install)
+
+    _resolve_source_tui_command(source_dir, "bun")
+    dependency.rmdir()
+    with pytest.raises(TuiUnavailableError, match="partial install"):
+        _resolve_source_tui_command(source_dir, "bun")
+    _resolve_source_tui_command(source_dir, "bun")
+
+    assert installs == 3
+
+
 def test_source_checkout_fails_when_locked_dependencies_cannot_be_refreshed(
     monkeypatch: pytest.MonkeyPatch,
     tmp_path: Path,