Fix invalid link targets aborting scans

Cargo.toml

@@ -20,3 +20,6 @@ tempfile = "3"
 [profile.dist]
 inherits = "release"
 lto = "thin"
+
+[target."cfg(unix)".dependencies]
+libc = "0.2"

README.md

@@ -131,7 +131,9 @@ Markdown reference labels are not filesystem targets and are not checked.
 
 Paths are checked literally: no automatic `.md` extension, website routing, or
 build-template expansion. Generated targets must already exist when checking;
-intentional broken links are reported too. There are no suppressions yet.
+intentional broken links are reported too. Invalid filenames and paths that are
+too long produce findings without stopping the scan. Other inspection failures,
+such as permission errors, remain execution errors. There are no suppressions yet.
 
 ## Development
 

src/rules/markdown.rs

@@ -61,6 +61,9 @@ pub(crate) fn check(path: &Path, source: &str) -> Result<Vec<Diagnostic>, String
                         {
                             Some(format!("Target {raw_path:?} does not exist"))
                         }
+                        Err(error) if invalid_path_error(&error) => {
+                            Some(format!("Target {raw_path:?} is an invalid path: {error}"))
+                        }
                         Err(error) => {
                             return Err(format!(
                                 "cannot inspect link target {} from {}: {error}",
@@ -88,6 +91,22 @@ pub(crate) fn check(path: &Path, source: &str) -> Result<Vec<Diagnostic>, String
     Ok(diagnostics)
 }
 
+fn invalid_path_error(error: &io::Error) -> bool {
+    if error.kind() == io::ErrorKind::InvalidInput {
+        return true;
+    }
+    #[cfg(unix)]
+    if error.raw_os_error() == Some(libc::ENAMETOOLONG) {
+        return true;
+    }
+    // ERROR_INVALID_NAME, ERROR_BAD_PATHNAME, ERROR_FILENAME_EXCED_RANGE.
+    #[cfg(windows)]
+    if matches!(error.raw_os_error(), Some(123 | 161 | 206)) {
+        return true;
+    }
+    false
+}
+
 fn has_scheme(destination: &str) -> bool {
     let Some((scheme, _)) = destination.split_once(':') else {
         return false;
@@ -103,6 +122,13 @@ mod tests {
     use super::*;
     use tempfile::TempDir;
 
+    #[test]
+    fn inaccessible_targets_are_not_invalid_paths() {
+        for kind in [io::ErrorKind::PermissionDenied, io::ErrorKind::Other] {
+            assert!(!invalid_path_error(&io::Error::from(kind)));
+        }
+    }
+
     fn project() -> TempDir {
         let root = tempfile::tempdir().unwrap();
         fs::create_dir(root.path().join("docs")).unwrap();

tests/invalid_link_paths.rs

@@ -0,0 +1,55 @@
+use std::{
+    fs,
+    path::Path,
+    process::{Command, Output},
+};
+
+fn run(path: &Path) -> Output {
+    Command::new(env!("CARGO_BIN_EXE_ryni"))
+        .arg("check")
+        .arg(path)
+        .output()
+        .unwrap()
+}
+
+fn write_file(root: &Path, name: &str, content: &str) {
+    let path = root.join(name);
+    fs::create_dir_all(path.parent().unwrap()).unwrap();
+    fs::write(path, content).unwrap();
+}
+
+#[test]
+fn invalid_link_paths_do_not_abort_remaining_links_or_files() {
+    let project = tempfile::tempdir().unwrap();
+    let root = project.path();
+    write_file(
+        root,
+        "a.md",
+        &format!("[Too long]({})\n[Missing](missing.txt)\n", "a".repeat(300)),
+    );
+    write_file(root, "z.md", "[Later](missing.txt)\n");
+    let output = run(root);
+    let stdout = String::from_utf8_lossy(&output.stdout);
+    assert_eq!(output.status.code(), Some(1), "{output:?}");
+    assert!(output.stderr.is_empty());
+    assert!(stdout.contains("z.md:1:1"), "{stdout}");
+    assert!(stdout.ends_with("Found 3 errors.\n"), "{stdout}");
+}
+
+#[test]
+fn nbsp_reference_destination_does_not_abort_scan() {
+    let project = tempfile::tempdir().unwrap();
+    let root = project.path();
+    write_file(
+        root,
+        "a.md",
+        "See [#1].\n\n[#1]:\u{a0}https://example.com/pull/1\n",
+    );
+    write_file(root, "z.md", "[Later](missing.txt)\n");
+    let output = run(root);
+    let stdout = String::from_utf8_lossy(&output.stdout);
+    assert_eq!(output.status.code(), Some(1), "{output:?}");
+    assert!(output.stderr.is_empty());
+    assert!(stdout.contains("z.md:1:1"), "{stdout}");
+    assert!(stdout.ends_with("Found 2 errors.\n"), "{stdout}");
+}

website/rules.md

@@ -45,5 +45,7 @@ Markdown reference labels are not filesystem targets and are not checked.
 
 Paths are checked literally: no automatic `.md` extension, website routing, or
 build-template expansion. Generated targets must already exist when checking;
-intentional broken links are reported too. There are no suppressions yet.
+intentional broken links are reported too. Invalid filenames and paths that are
+too long produce findings without stopping the scan. Other inspection failures,
+such as permission errors, remain execution errors. There are no suppressions yet.