Show paths of config files when configurations contain errors

This addresses issue #3317, where as discussed we want to show the paths to
configuration files if they contain errors, to make it easier for the user to
locate them.

CHANGELOG.md

@@ -17,6 +17,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### New features
 
+* Show paths to config files when configuration errors occur
+
 ### Fixed bugs
 
 ## [0.18.0] - 2024-06-05

cli/src/cli_util.rs

@@ -2828,11 +2828,21 @@ impl CliRunner {
         let maybe_cwd_workspace_loader = WorkspaceLoader::init(find_workspace_dir(&cwd))
             .map_err(|err| map_workspace_load_error(err, None));
         layered_configs.read_user_config()?;
+        let mut repo_config_path = None;
         if let Ok(loader) = &maybe_cwd_workspace_loader {
             layered_configs.read_repo_config(loader.repo_path())?;
+            repo_config_path = Some(layered_configs.repo_config_path(loader.repo_path()));
         }
         let config = layered_configs.merge();
-        ui.reset(&config)?;
+        ui.reset(&config).map_err(|e| {
+            let user_config_path = layered_configs.user_config_path().unwrap_or(None);
+            let paths = [repo_config_path, user_config_path]
+                .into_iter()
+                .flatten()
+                .map(|path| format!("- {}", path.display()))
+                .join("\n");
+            e.hinted(format!("Check the following config files:\n{}", paths))
+        })?;
 
         let string_args = expand_args(ui, &self.app, env::args_os(), &config)?;
         let (matches, args) = parse_args(

cli/src/config.rs

@@ -228,12 +228,20 @@ impl LayeredConfigs {
         Ok(())
     }
 
+    pub fn user_config_path(&self) -> Result<Option<PathBuf>, ConfigError> {
+        existing_config_path()
+    }
+
     #[instrument]
     pub fn read_repo_config(&mut self, repo_path: &Path) -> Result<(), ConfigError> {
-        self.repo = Some(read_config_file(&repo_path.join("config.toml"))?);
+        self.repo = Some(read_config_file(&self.repo_config_path(repo_path))?);
         Ok(())
     }
 
+    pub fn repo_config_path(&self, repo_path: &Path) -> PathBuf {
+        repo_path.join("config.toml")
+    }
+
     pub fn parse_config_args(&mut self, toml_strs: &[String]) -> Result<(), ConfigError> {
         let config = toml_strs
             .iter()

cli/tests/test_config_command.rs

@@ -833,6 +833,28 @@ fn test_config_path_syntax() {
     "###);
 }
 
+#[test]
+fn test_config_show_paths() {
+    let mut test_env = TestEnvironment::default();
+    test_env.jj_cmd_ok(test_env.env_root(), &["git", "init", "repo"]);
+    let user_config_path = test_env.config_path().join("config.toml");
+    test_env.set_config_path(user_config_path.to_owned());
+    let repo_path = test_env.env_root().join("repo");
+
+    test_env.jj_cmd_ok(
+        &repo_path,
+        &["config", "set", "--user", "ui.paginate", ":builtin"],
+    );
+    let stderr = test_env.jj_cmd_failure(test_env.env_root(), &["st"]);
+    insta::assert_snapshot!(stderr, @r###"
+    Config error: Invalid `ui.paginate`
+    Caused by: enum PaginationChoice does not have variant constructor :builtin
+    Hint: Check the following config files:
+    - $TEST_ENV/config/config.toml
+    For help, see https://github.com/martinvonz/jj/blob/main/docs/config.md.
+    "###);
+}
+
 fn find_stdout_lines(keyname_pattern: &str, stdout: &str) -> String {
     let key_line_re = Regex::new(&format!(r"(?m)^{keyname_pattern} = .*$")).unwrap();
     key_line_re