fix(cli): fix panic when using --config option

Closes #332

Author: JamieMason

src/cli.rs

@@ -7,6 +7,10 @@ use {
   std::{env, path::PathBuf},
 };
 
+#[cfg(test)]
+#[path = "cli_test.rs"]
+mod cli_test;
+
 #[derive(Debug)]
 pub enum Subcommand {
   Fix,
@@ -314,9 +318,31 @@ fn create() -> Command {
 }
 
 fn config_option(_command: &str) -> Arg {
-  Arg::new("config").long("config").value_name("PATH").long_help(cformat!(
-    r#"Path to a specific config file to use. When set, config file discovery is skipped."#
-  ))
+  Arg::new("config")
+    .long("config")
+    .value_name("PATH")
+    .value_parser(ValueParser::new(parse_config_path))
+    .long_help(cformat!(
+      r#"Path to a specific config file to use. When set, config file discovery is skipped."#
+    ))
+}
+
+fn parse_config_path(raw: &str) -> Result<PathBuf, String> {
+  let path = PathBuf::from(raw);
+  let resolved = if path.is_absolute() {
+    path.clone()
+  } else {
+    env::current_dir()
+      .map_err(|e| format!("could not resolve current directory: {e}"))?
+      .join(&path)
+  };
+  if !resolved.exists() {
+    return Err(format!("file not found: {}", path.display()));
+  }
+  if !resolved.is_file() {
+    return Err(format!("not a file: {}", path.display()));
+  }
+  Ok(path)
 }
 
 fn dependencies_option(command: &str) -> Arg {

src/cli_test.rs

@@ -0,0 +1,51 @@
+use {
+  crate::cli::Cli,
+  std::{env, fs, path::PathBuf},
+};
+
+fn write_temp_config(name: &str) -> PathBuf {
+  let path = env::temp_dir().join(format!("syncpack-cli-test-{}-{name}", std::process::id()));
+  fs::write(&path, "{}").expect("write temp config");
+  path
+}
+
+#[test]
+fn config_flag_accepts_existing_file() {
+  let temp = write_temp_config("ok.json");
+  let args = ["syncpack", "lint", "--config", temp.to_str().unwrap()]
+    .iter()
+    .map(|s| s.to_string())
+    .collect::<Vec<_>>();
+
+  let cli = Cli::parse(&args).expect("--config should parse");
+  let config_path = cli.config_path.expect("config_path should be Some");
+  assert!(config_path.is_absolute());
+  assert_eq!(config_path, temp);
+
+  let _ = fs::remove_file(&temp);
+}
+
+#[test]
+fn config_flag_rejects_missing_file_with_clap_error() {
+  let args = ["syncpack", "lint", "--config", "definitely-not-a-real-file.ts"]
+    .iter()
+    .map(|s| s.to_string())
+    .collect::<Vec<_>>();
+
+  let err = Cli::parse(&args).expect_err("missing file must be rejected");
+  let msg = format!("{err:?}");
+  assert!(msg.contains("file not found"), "expected clap-style error, got: {msg}");
+}
+
+#[test]
+fn config_flag_rejects_directory_with_clap_error() {
+  let dir = env::temp_dir();
+  let args = ["syncpack", "lint", "--config", dir.to_str().unwrap()]
+    .iter()
+    .map(|s| s.to_string())
+    .collect::<Vec<_>>();
+
+  let err = Cli::parse(&args).expect_err("directory must be rejected");
+  let msg = format!("{err:?}");
+  assert!(msg.contains("not a file"), "expected clap-style error, got: {msg}");
+}