rework ldns command matching to use file-stem and give errors

src/lib.rs

@@ -19,19 +19,55 @@ pub fn try_ldns_compatibility<I: IntoIterator<Item = OsString>>(
     let mut args_iter = args.into_iter();
     let binary_path = args_iter.next().ok_or("Missing binary name")?;
 
-    let binary_name = Path::new(&binary_path)
+    let binary_name = extract_binary_name(Path::new(&binary_path))?;
+
+    // We only branch on the binary name for the ldns utilities. The rest we
+    // just handle as regular dnst.
+    let Some(binary_name) = binary_name.strip_prefix("ldns-") else {
+        return Ok(None);
+    };
+
+    let res = match binary_name {
+        "key2ds" => Key2ds::parse_ldns_args(args_iter),
+        "nsec3-hash" => Nsec3Hash::parse_ldns_args(args_iter),
+        _ => return Err(format!("Unrecognized ldns command 'ldns-{binary_name}'").into()),
+    };
+
+    Ok(Some(res?))
+}
+
+/// Get the binary name from a [`Path`].
+///
+/// The binary name is the file name without any extensions. It is similar
+/// to the unstable `Path::file_stem`.
+///
+/// ```rust
+/// use dnst::extract_binary_name;
+/// use std::path::Path;
+///
+/// let bin = extract_binary_name(Path::new("foo/ldns-xxx")).unwrap();
+/// assert_eq!(bin, "ldns-xxx");
+///
+/// let bin = extract_binary_name(Path::new("foo/ldns-xxx.real")).unwrap();
+/// assert_eq!(bin, "ldns-xxx");
+///
+/// let bin = extract_binary_name(Path::new("./ldns-xxx.exe")).unwrap();
+/// assert_eq!(bin, "ldns-xxx");
+///
+/// let bin = extract_binary_name(Path::new("ldns-xxx")).unwrap();
+/// assert_eq!(bin, "ldns-xxx");
+/// ```
+pub fn extract_binary_name(path: &Path) -> Result<&str, Error> {
+    let filename = path
         .file_name()
         .ok_or("Missing binary file name")?
         .to_str()
         .ok_or("Binary file name is not valid unicode")?;
 
-    let res = match binary_name {
-        "ldns-key2ds" => Key2ds::parse_ldns_args(args_iter),
-        "ldns-nsec3-hash" => Nsec3Hash::parse_ldns_args(args_iter),
-        _ => return Ok(None),
-    };
-
-    res.map(Some)
+    match filename.split_once('.') {
+        Some((binary, _)) => Ok(binary),
+        None => Ok(filename),
+    }
 }
 
 fn parse_args(env: impl Env) -> Result<Args, Error> {