fix(compiler): unexpected StripPrefixError

packages/@winglang/wingc/src/lib.rs

@@ -328,6 +328,23 @@ pub fn find_nearest_wing_project_dir(source_path: &Utf8Path) -> Utf8PathBuf {
 	return initial_dir;
 }
 
+fn common_path(path1: &Utf8Path, path2: &Utf8Path) -> Utf8PathBuf {
+	assert!(path1.is_absolute(), "path1 must be absolute");
+	assert!(path2.is_absolute(), "path2 must be absolute");
+
+	let components1: Vec<_> = path1.components().collect();
+	let components2: Vec<_> = path2.components().collect();
+
+	let common_prefix = components1
+		.iter()
+		.zip(components2.iter())
+		.take_while(|&(a, b)| a == b)
+		.map(|(component, _)| component)
+		.collect::<Vec<_>>();
+
+	common_prefix.into_iter().collect()
+}
+
 pub fn compile(source_path: &Utf8Path, source_text: Option<String>, out_dir: &Utf8Path) -> Result<CompilerOutput, ()> {
 	let project_dir = find_nearest_wing_project_dir(source_path);
 	let source_package = as_wing_library(&project_dir, false).unwrap_or_else(|| DEFAULT_PACKAGE_NAME.to_string());
@@ -336,7 +353,7 @@ pub fn compile(source_path: &Utf8Path, source_text: Option<String>, out_dir: &Ut
 
 	// A map from package names to their root directories
 	let mut library_roots: IndexMap<String, Utf8PathBuf> = IndexMap::new();
-	library_roots.insert(source_package, project_dir.to_owned());
+	library_roots.insert(source_package.clone(), project_dir.to_owned());
 
 	// -- PARSING PHASE --
 	let mut files = Files::new();
@@ -353,6 +370,22 @@ pub fn compile(source_path: &Utf8Path, source_text: Option<String>, out_dir: &Ut
 		&mut asts,
 	);
 
+	// If there's no wing.toml or package.json, then we don't know for sure where the root
+	// of the project is, so we simply find the common root of all files that are part of the
+	// default package.
+	if source_package == DEFAULT_PACKAGE_NAME {
+		let mut common_root = project_dir.to_owned();
+		for file in &topo_sorted_files {
+			if file.package != source_package {
+				continue;
+			}
+
+			common_root = common_path(&common_root, &file.path);
+		}
+		// Update the source package to be the common root
+		library_roots.insert(source_package.clone(), common_root);
+	}
+
 	emit_warning_for_unsupported_package_managers(&project_dir);
 
 	// -- DESUGARING PHASE --

packages/@winglang/wingc/src/type_check.rs

@@ -7496,27 +7496,58 @@ fn lookup_known_type(name: &'static str, env: &SymbolEnv) -> TypeRef {
 /// ```
 pub fn calculate_fqn_for_namespace(package_name: &str, package_root: &Utf8Path, path: &Utf8Path) -> String {
 	let normalized_root = normalize_path(&package_root, None);
-	let normalized = normalize_path(&path, None);
-	if normalized.starts_with("..") {
-		panic!(
-			"File path \"{}\" is not within the package root \"{}\"",
-			path, package_root
-		);
+	let normalized_path = normalize_path(&path, None);
+	if normalized_path.starts_with("..") {
+		report_diagnostic(Diagnostic {
+			message: format!(
+				"File path \"{}\" is not within the package root \"{}\"",
+				path, package_root
+			),
+			span: None,
+			annotations: vec![],
+			hints: vec![],
+			severity: DiagnosticSeverity::Error,
+		});
+		return package_name.to_string();
 	}
+
 	let assembly = package_name;
-	let normalized = if normalized.as_str().ends_with(".w") {
-		normalized.parent().expect("Expected a parent directory")
+	let normalized_dir = if normalized_path.as_str().ends_with(".w") {
+		if let Some(normalized_parent) = normalized_path.parent() {
+			normalized_parent
+		} else {
+			report_diagnostic(Diagnostic {
+				message: format!("Source file \"{}\" does not have a parent directory", path),
+				span: None,
+				annotations: vec![],
+				hints: vec![],
+				severity: DiagnosticSeverity::Error,
+			});
+			return package_name.to_string();
+		}
 	} else {
-		&normalized
+		&normalized_path
 	};
-	let relative_path = normalized
-		.strip_prefix(&normalized_root)
-		.expect(format!("not a prefix: {} {}", normalized_root, normalized).as_str());
-	if relative_path == Utf8Path::new("") {
-		return assembly.to_string();
-	}
-	let namespace = relative_path.as_str().replace("/", ".");
-	format!("{}.{}", assembly, namespace)
+
+	if let Ok(relative_path) = normalized_dir.strip_prefix(&normalized_root) {
+		if relative_path == Utf8Path::new("") {
+			return assembly.to_string();
+		}
+		let namespace = relative_path.as_str().replace("/", ".");
+		return format!("{}.{}", assembly, namespace);
+	} else {
+		report_diagnostic(Diagnostic {
+			message: format!(
+				"Source file \"{}\" is not within the package root \"{}\"",
+				path, package_root
+			),
+			span: None,
+			annotations: vec![],
+			hints: vec![],
+			severity: DiagnosticSeverity::Error,
+		});
+		return package_name.to_string();
+	}
 }
 
 #[derive(Debug)]

tests/valid/subdir/bring_outer.main.w

@@ -0,0 +1 @@
+bring "../baz.w" as baz;