fix: lint gate returns SKIPPED when linter binary is missing (#372)

codeframe/core/gates.py

@@ -637,8 +637,9 @@ def run_lint_on_file(
     """Run the appropriate linter on a single file.
 
     Returns a ``GateCheck`` with status PASSED / FAILED / SKIPPED / ERROR.
-    SKIPPED is returned when no linter is registered for the file extension
-    or the required binary is not installed.
+    SKIPPED is returned when no linter is registered for the file extension,
+    the required binary is not installed, or the tool is not found in the
+    project's dependencies (e.g. ``uv run ruff`` fails to spawn).
     """
     import time
 
@@ -674,6 +675,30 @@ def run_lint_on_file(
             output += "\n" + result.stderr
         output = output.strip()
 
+        # Detect tool-not-found: uv/shell report "Failed to spawn",
+        # "command not found", or "No such file or directory" when the
+        # linter binary isn't installed in the target project.
+        # Note: "no such file or directory" is only matched when the tool
+        # name also appears in stderr, to avoid false positives from
+        # missing *target* files.
+        if result.returncode != 0 and result.stderr:
+            stderr_lower = result.stderr.lower()
+            tool_names = {cfg.cmd[0].lower(), cfg.name.lower()}
+            if (
+                "failed to spawn" in stderr_lower
+                or "command not found" in stderr_lower
+                or (
+                    "no such file or directory" in stderr_lower
+                    and any(name in stderr_lower for name in tool_names)
+                )
+            ):
+                return GateCheck(
+                    name=cfg.name,
+                    status=GateStatus.SKIPPED,
+                    output=f"{cfg.name} not found in project dependencies",
+                    duration_ms=duration_ms,
+                )
+
         passed = result.returncode == 0
         check = GateCheck(
             name=cfg.name,

tests/core/test_gates_observability.py

@@ -1,5 +1,6 @@
 """Tests for gate observability enhancements."""
 
+import subprocess
 from pathlib import Path
 from unittest.mock import patch
 
@@ -254,3 +255,25 @@ def test_missing_linter_binary_skips(self, mock_which, tmp_path):
 
         check = run_lint_on_file(py_file, tmp_path)
         assert check.status == GateStatus.SKIPPED
+
+    @patch("codeframe.core.gates.subprocess.run")
+    @patch("codeframe.core.gates.shutil.which")
+    def test_uv_run_missing_tool_returns_skipped(self, mock_which, mock_run, tmp_path):
+        """When uv run fails because the linter isn't a project dependency, return SKIPPED."""
+        py_file = tmp_path / "test.py"
+        py_file.write_text("x = 1\n")
+
+        # ruff not on PATH but uv is → gates proceeds with 'uv run ruff'
+        mock_which.side_effect = lambda cmd: "/usr/bin/uv" if cmd == "uv" else None
+
+        # Simulate uv failing to spawn ruff (exit code 2)
+        mock_run.return_value = subprocess.CompletedProcess(
+            args=["uv", "run", "ruff", "check", str(py_file)],
+            returncode=2,
+            stdout="",
+            stderr="error: Failed to spawn: `ruff`\nCaused by: No such file or directory (os error 2)",
+        )
+
+        check = run_lint_on_file(py_file, tmp_path)
+        assert check.status == GateStatus.SKIPPED
+        assert "not found" in check.output.lower()