[core] Lint duplicate UNIT_/CONF_ constants against both const homes (#19422)

tests/script/test_ci_custom.py

@@ -151,6 +151,82 @@ def test_nolint_on_control_line_suppresses() -> None:
     assert not _lint("if (x)  // NOLINT\n  ESP_LOGD(t);\n")
 
 
+# --- rule: UNIT_ constants must not be redefined (mirror of the CONF_ check) ---
+
+# Real UNIT_ constants that live in each canonical home.
+UNIT_IN_CONST_PY = ci_custom.UNIT_CONSTANTS[0]
+UNIT_IN_COMPONENT_CONST = ci_custom.COMPONENT_UNIT_CONSTANTS[0]
+
+
+def _unit_def(fname: str, content: str) -> list:
+    return ci_custom.lint_unit_from_const_py(fname, content)
+
+
+def test_unit_already_in_const_py_is_flagged() -> None:
+    errs = _unit_def("esphome/components/x/sensor.py", f'{UNIT_IN_CONST_PY} = "x"\n')
+    assert errs
+    assert "const.py" in errs[0][2]
+
+
+def test_unit_already_in_component_const_is_flagged() -> None:
+    errs = _unit_def(
+        "esphome/components/x/sensor.py", f'{UNIT_IN_COMPONENT_CONST} = "x"\n'
+    )
+    assert errs
+    assert "esphome.components.const" in errs[0][2]
+
+
+def test_unit_not_in_const_py_is_tracked_not_flagged() -> None:
+    ci_custom.UNIT_CONSTANTS_USES.clear()
+    assert _unit_def("a.py", 'UNIT_FOO_BAR = "fb"\n') == []
+    assert ci_custom.UNIT_CONSTANTS_USES["UNIT_FOO_BAR"] == ["a.py"]
+
+
+def test_unit_defined_in_three_files_is_flagged() -> None:
+    ci_custom.UNIT_CONSTANTS_USES.clear()
+    for fname in ("a.py", "b.py", "c.py"):
+        _unit_def(fname, 'UNIT_FOO_BAR = "fb"\n')
+    errs = ci_custom.lint_unit_constants_usage()
+    assert any("UNIT_FOO_BAR" in e and "3 files" in e for e in errs)
+
+
+def test_unit_defined_in_two_files_is_not_flagged() -> None:
+    ci_custom.UNIT_CONSTANTS_USES.clear()
+    for fname in ("a.py", "b.py"):
+        _unit_def(fname, 'UNIT_FOO_BAR = "fb"\n')
+    assert ci_custom.lint_unit_constants_usage() == []
+
+
+# --- same rule for CONF_, now also recognising the components/const home ---
+
+CONF_IN_CONST_PY = ci_custom.CONSTANTS[0]
+CONF_IN_COMPONENT_CONST = ci_custom.COMPONENT_CONSTANTS[0]
+
+
+def _conf_def(fname: str, content: str) -> list:
+    return ci_custom.lint_conf_from_const_py(fname, content)
+
+
+def test_conf_already_in_const_py_is_flagged() -> None:
+    errs = _conf_def("esphome/components/x/sensor.py", f'{CONF_IN_CONST_PY} = "x"\n')
+    assert errs
+    assert "const.py" in errs[0][2]
+
+
+def test_conf_already_in_component_const_is_flagged() -> None:
+    errs = _conf_def(
+        "esphome/components/x/sensor.py", f'{CONF_IN_COMPONENT_CONST} = "x"\n'
+    )
+    assert errs
+    assert "esphome.components.const" in errs[0][2]
+
+
+def test_conf_not_in_a_const_home_is_tracked_not_flagged() -> None:
+    ci_custom.CONSTANTS_USES.pop("CONF_FOO_BAR", None)
+    assert _conf_def("a.py", 'CONF_FOO_BAR = "foo_bar"\n') == []
+    assert ci_custom.CONSTANTS_USES["CONF_FOO_BAR"] == ["a.py"]
+
+
 # --- ESP_LOG call scanner and bare-literal-ternary lint ---