Preserve URL fragments in OpenFile / Windows OpenURL

browser.go

@@ -7,9 +7,11 @@ import (
 	"fmt"
 	"io"
 	"io/ioutil"
+	"net/url"
 	"os"
 	"os/exec"
 	"path/filepath"
+	"strings"
 )
 
 // Stdout is the io.Writer to which executed commands write standard output.
@@ -19,12 +21,34 @@ var Stdout io.Writer = os.Stdout
 var Stderr io.Writer = os.Stderr
 
 // OpenFile opens new browser window for the file path.
+// A URL fragment after '#' (for example "index.html#section") is preserved.
 func OpenFile(path string) error {
-	path, err := filepath.Abs(path)
+	path, frag := splitFragment(path)
+	abs, err := filepath.Abs(path)
 	if err != nil {
 		return err
 	}
-	return OpenURL("file://" + path)
+	return OpenURL(fileURL(abs, frag))
+}
+
+// splitFragment separates a filesystem path from an optional URL fragment.
+func splitFragment(path string) (file, fragment string) {
+	i := strings.LastIndex(path, "#")
+	if i < 0 {
+		return path, ""
+	}
+	return path[:i], path[i+1:]
+}
+
+// fileURL builds a file: URL for an absolute filesystem path, with optional fragment.
+func fileURL(absPath, fragment string) string {
+	p := filepath.ToSlash(absPath)
+	if !strings.HasPrefix(p, "/") {
+		// Windows drive path, e.g. C:/foo → /C:/foo
+		p = "/" + p
+	}
+	u := url.URL{Scheme: "file", Path: p, Fragment: fragment}
+	return u.String()
 }
 
 // OpenReader consumes the contents of r and presents the

browser_test.go

@@ -0,0 +1,32 @@
+package browser
+
+import (
+	"strings"
+	"testing"
+)
+
+func TestSplitFragment(t *testing.T) {
+	file, frag := splitFragment(`c:\some-file.html#basic`)
+	if file != `c:\some-file.html` {
+		t.Fatalf("file = %q", file)
+	}
+	if frag != "basic" {
+		t.Fatalf("frag = %q", frag)
+	}
+	f2, g2 := splitFragment("index.html")
+	if f2 != "index.html" || g2 != "" {
+		t.Fatalf("got %q %q", f2, g2)
+	}
+}
+
+func TestFileURLPreservesFragment(t *testing.T) {
+	got := fileURL("/tmp/doc.html", "basic")
+	want := "file:///tmp/doc.html#basic"
+	if got != want {
+		t.Fatalf("got %q want %q", got, want)
+	}
+	got = fileURL("C:/some-file.html", "basic")
+	if !strings.HasPrefix(got, "file:///C:/some-file.html") || !strings.HasSuffix(got, "#basic") {
+		t.Fatalf("windows-style got %q", got)
+	}
+}

browser_windows.go

@@ -1,7 +1,6 @@
 package browser
 
-import "golang.org/x/sys/windows"
-
+// Windows ShellExecute drops fragments on file: URLs. FileProtocolHandler keeps them.
 func openBrowser(url string) error {
-	return windows.ShellExecute(0, nil, windows.StringToUTF16Ptr(url), nil, nil, windows.SW_SHOWNORMAL)
+	return runCmd("rundll32", "url.dll,FileProtocolHandler", url)
 }