fix: 423 missing file message (#558)

crates/cli_bin/fixtures/pattern_non_existent/.grit/grit.yaml

@@ -0,0 +1,3 @@
+version: 0.0.1
+patterns:
+  - file: patterns/non_existent.md

crates/cli_bin/tests/patterns_test.rs

@@ -180,6 +180,27 @@ fn fails_recursion() -> Result<()> {
     Ok(())
 }
 
+#[test]
+fn fails_to_find_non_existent_file() -> Result<()> {
+    let (_temp_dir, temp_fixture_path) = get_fixture("pattern_non_existent", false)?;
+
+    let mut cmd = get_test_cmd()?;
+    cmd.arg("patterns")
+        .arg("test")
+        .current_dir(&temp_fixture_path);
+    let output = cmd.output()?;
+    let stdout = String::from_utf8(output.stdout)?;
+    let stderr = String::from_utf8(output.stderr)?;
+    println!("stdout: {}", stdout);
+    println!("stderr: {}", stderr);
+
+    assert!(
+        stderr.contains("Failed to find pattern at .grit/patterns/non_existent.md. Does it exist?")
+    );
+
+    Ok(())
+}
+
 #[test]
 fn test_multifile_fails_if_unchanged_file_has_incorrect_expected() -> Result<()> {
     let (_temp_dir, fixture_dir) = get_fixture("test_multifile_fail", true)?;

crates/gritmodule/src/parser.rs

@@ -98,10 +98,17 @@ pub async fn get_patterns_from_file(
     ext: PatternFileExt,
     overrides: GritDefinitionOverrides,
 ) -> Result<Vec<ModuleGritPattern>> {
-    let repo_root = find_repo_root_from(path.clone()).await?;
-    let content = fs::read_to_string(&path).await?;
+    let path_str = path.to_string_lossy();
+    let repo_root = find_repo_root_from(path.clone()).await.context(format!(
+        "Failed to find repository root from path {}",
+        path_str
+    ))?;
+    let content = fs::read_to_string(&path).await.context(format!(
+        "Failed to find pattern at {}. Does it exist?",
+        extract_relative_path(&path_str, &repo_root)
+    ))?;
     let mut file = RichFile {
-        path: path.to_string_lossy().to_string(),
+        path: path_str.to_string(),
         content,
     };
     ext.get_patterns(&mut file, &source_module, &repo_root, overrides)