fix(lsp): handle Windows file URIs correctly

On Windows, file URIs must use the format file:///C:/path (with three slashes
and forward slashes). The URL parser produces paths like /C:/path which need
the leading slash stripped to be valid Windows paths.

- Use url.URL to construct proper file:// URIs in tests
- Handle leading slash before drive letter when parsing Windows file URIs
- Normalize path separators for cross-platform compatibility

Author: jupblb

internal/lsp/server.go

@@ -290,6 +290,13 @@ func (s *Server) uriToRepoPath(uri string) (string, error) {
 	}
 
 	absPath := parsed.Path
+	// On Windows, file URIs like file:///C:/path produce a path like "/C:/path".
+	// We need to strip the leading slash to get a valid Windows path.
+	if len(absPath) >= 3 && absPath[0] == '/' && absPath[2] == ':' {
+		absPath = absPath[1:]
+	}
+	// Convert forward slashes to the native path separator
+	absPath = filepath.FromSlash(absPath)
 
 	gitRoot, err := getGitRoot()
 	if err != nil {
@@ -301,7 +308,8 @@ func (s *Server) uriToRepoPath(uri string) (string, error) {
 		return "", errors.Wrap(err, "failed to compute relative path")
 	}
 
-	return relPath, nil
+	// Ensure we always return forward slashes for consistency
+	return filepath.ToSlash(relPath), nil
 }
 
 func getGitRoot() (string, error) {

internal/lsp/server_test.go

@@ -2,6 +2,7 @@ package lsp
 
 import (
 	"context"
+	"net/url"
 	"os"
 	"path/filepath"
 	"testing"
@@ -12,6 +13,16 @@ import (
 	"github.com/stretchr/testify/require"
 )
 
+// pathToFileURI converts a file path to a proper file:// URI that works on all platforms.
+// On Windows, this properly handles drive letters (e.g., C:\path -> file:///C:/path).
+func pathToFileURI(path string) string {
+	u := url.URL{
+		Scheme: "file",
+		Path:   filepath.ToSlash(path),
+	}
+	return u.String()
+}
+
 func TestUriToRepoPath(t *testing.T) {
 	gitRoot, err := getGitRoot()
 	require.NoError(t, err)
@@ -23,17 +34,17 @@ func TestUriToRepoPath(t *testing.T) {
 	}{
 		{
 			name:     "simple file URI",
-			uri:      "file://" + filepath.Join(gitRoot, "cmd/src/main.go"),
+			uri:      pathToFileURI(filepath.Join(gitRoot, "cmd/src/main.go")),
 			wantPath: "cmd/src/main.go",
 		},
 		{
 			name:     "nested path",
-			uri:      "file://" + filepath.Join(gitRoot, "internal/lsp/server.go"),
+			uri:      pathToFileURI(filepath.Join(gitRoot, "internal/lsp/server.go")),
 			wantPath: "internal/lsp/server.go",
 		},
 		{
 			name:     "root file",
-			uri:      "file://" + filepath.Join(gitRoot, "go.mod"),
+			uri:      pathToFileURI(filepath.Join(gitRoot, "go.mod")),
 			wantPath: "go.mod",
 		},
 	}
@@ -266,7 +277,7 @@ func TestHandleTextDocumentDocumentHighlight(t *testing.T) {
 				commit:    "abc123",
 			}
 
-			uri := "file://" + filepath.Join(gitRoot, tt.path)
+			uri := pathToFileURI(filepath.Join(gitRoot, tt.path))
 			params := &protocol.DocumentHighlightParams{
 				TextDocumentPositionParams: protocol.TextDocumentPositionParams{
 					TextDocument: protocol.TextDocumentIdentifier{URI: uri},