fix(cfg): show only the duplicate-key warning, once

docs/guide/cli-reference.md

@@ -339,7 +339,7 @@ unshackle cfg [KEY] [VALUE] [OPTIONS]
 | `--list` | List all set configuration values. |
 
 !!! warning "Comments are stripped"
-    Writing a value through `cfg` rewrites the configuration file and **removes all comments** from it. If your config relies on comments, edit it by hand instead. Setting a value and using `--unset` together is an error. If a config key is set twice in the same block, `cfg` stops and gives the line numbers of the two copies. Other commands warn with the same line numbers and use the later copy.
+    Writing a value through `cfg` rewrites the configuration file and **removes all comments** from it. If your config relies on comments, edit it by hand instead. Setting a value and using `--unset` together is an error. If a config key is set twice in the same block, every command warns with the line numbers of the two copies and uses the later copy. `cfg` stops without a change.
 
 !!! example
     ```shell

tests/commands/test_cfg.py

@@ -1,5 +1,6 @@
 from __future__ import annotations
 
+import logging
 from pathlib import Path
 
 import pytest
@@ -15,19 +16,25 @@ def config_file(tmp_path: Path, monkeypatch: pytest.MonkeyPatch) -> Path:
     return path
 
 
-def test_a_duplicate_key_names_its_lines_but_no_key_or_value(config_file: Path) -> None:
+def test_a_duplicate_key_logs_its_lines_once_and_names_no_key_or_value(
+    config_file: Path, caplog: pytest.LogCaptureFixture
+) -> None:
     config_file.write_text(
         "theme: rainbow\ncredentials:\n  EXAMPLE: first-secret\n  OTHER: other\n  EXAMPLE: second-secret\n"
         "serve:\n  users:\n    key-secret: {tier: a}\n    key-secret: {tier: b}\n",
         encoding="utf-8",
     )
-    result = CliRunner().invoke(cfg_module.cfg, ["theme"])
+    with caplog.at_level(logging.WARNING, logger="config"):
-    assert isinstance(result.exception, SystemExit), result.exception  # a ClickException, not a crash
+        result = CliRunner().invoke(cfg_module.cfg, ["theme"])
+        CliRunner().invoke(cfg_module.cfg, ["theme"])
+    assert isinstance(result.exception, SystemExit), result.exception
     assert result.exit_code == 1
-    text = " ".join(result.output.replace("│", " ").split())  # the error panel wraps its lines
+    assert caplog.messages == [
-    assert "unshackle.yaml: duplicate key on lines 3 and 5, lines 8 and 9. Unshackle uses the later one." in text
+        f"{config_file}: duplicate key on lines 3 and 5, lines 8 and 9. Unshackle uses the later one."
-    assert "secret" not in result.output
+    ]
-    assert "EXAMPLE" not in result.output
+    assert "Error" not in result.output and "lines" not in result.output
+    for output in (result.output, caplog.text):
+        assert "secret" not in output and "EXAMPLE" not in output
 
 
 def test_a_duplicate_key_blocks_a_write(config_file: Path) -> None:
@@ -45,7 +52,9 @@ def test_a_valid_config_still_reads_a_key(config_file: Path) -> None:
     assert "rainbow" in result.output
 
 
-def test_a_duplicate_only_ruamel_sees_still_gives_its_line(config_file: Path) -> None:
+def test_a_duplicate_only_ruamel_sees_still_gives_its_line(config_file: Path, caplog: pytest.LogCaptureFixture) -> None:
     config_file.write_text("a: 1\n1: x\n0x1: y\n", encoding="utf-8")
-    result = CliRunner().invoke(cfg_module.cfg, ["a"])
+    with caplog.at_level(logging.WARNING):
-    assert "unshackle.yaml: duplicate key on line 3." in " ".join(result.output.replace("│", " ").split())
+        result = CliRunner().invoke(cfg_module.cfg, ["a"])
+    assert result.exit_code == 1
+    assert caplog.messages == [f"{config_file}: duplicate key on line 3. Unshackle uses the later one."]

unshackle/commands/cfg.py

@@ -6,7 +6,7 @@ import click
 from ruamel.yaml import YAML
 from ruamel.yaml.constructor import DuplicateKeyError
 
-from unshackle.core.config import config, duplicate_key_lines, duplicate_key_message, get_config_path
+from unshackle.core.config import config, duplicate_key_lines, get_config_path, load_yaml
 from unshackle.core.constants import context_settings
 
 
@@ -45,10 +45,13 @@ def cfg(ctx: click.Context, key: str, value: str, unset: bool, list_: bool) -> N
         try:
             data = yaml.load(config_path)
         except DuplicateKeyError as e:
-            pairs = duplicate_key_lines(yaml.compose(config_path))
+            if duplicate_key_lines(yaml.compose(config_path)):
-            raise click.ClickException(
+                load_yaml(config_path)
-                duplicate_key_message(config_path.name, pairs, e.problem_mark.line + 1)
+            else:
-            ) from None
+                log.warning(
+                    f"{config_path}: duplicate key on line {e.problem_mark.line + 1}. Unshackle uses the later one."
+                )
+            sys.exit(1)
 
     if not data:
         log.warning("No config file was found or it has no data, yet")

unshackle/core/config.py

@@ -406,12 +406,6 @@ def duplicate_key_lines(root: Any) -> list[tuple[int, int]]:
     return sorted(pairs)
 
 
-def duplicate_key_message(name: str, pairs: list[tuple[int, int]], line: int = 0) -> str:
-    """Say where a file repeats a key: each (first, repeat) pair, or `line` when no pair is known."""
-    where = ", ".join(f"lines {first} and {repeat}" for first, repeat in pairs) or f"line {line}"
-    return f"{name}: duplicate key on {where}. Unshackle uses the later one."
-
-
 _warned: set[str] = set()
 
 
@@ -422,9 +416,12 @@ def load_yaml(path: Path) -> Any:
         node = loader.get_single_node()
         if node is None:
             return None
-        if (pairs := duplicate_key_lines(node)) and (message := duplicate_key_message(str(path), pairs)) not in _warned:
+        if pairs := duplicate_key_lines(node):
-            _warned.add(message)
+            where = ", ".join(f"lines {first} and {repeat}" for first, repeat in pairs)
-            logging.getLogger("config").warning(message)
+            message = f"{path}: duplicate key on {where}. Unshackle uses the later one."
+            if message not in _warned:
+                _warned.add(message)
+                logging.getLogger("config").warning(message)
         return loader.construct_document(node)
     finally:
         loader.dispose()