From 91bd68cdc575c54931c7fdd0fda4834c5fe0445d Mon Sep 17 00:00:00 2001
From: Nicolas MASSE <nicolas.masse@itix.fr>
Date: Fri, 13 Nov 2020 20:33:22 +0100
Subject: [PATCH] fix bug in file:// url parsing

---
 url_checker.go      | 24 ++++++++++++++++++++++--
 url_checker_test.go |  5 ++++-
 2 files changed, 26 insertions(+), 3 deletions(-)

diff --git a/url_checker.go b/url_checker.go
index 8f40948..5ba19d8 100644
--- a/url_checker.go
+++ b/url_checker.go
@@ -9,6 +9,7 @@ import (
 	"path"
 	"path/filepath"
 	"regexp"
+	"strings"
 	"sync"
 	"time"
 
@@ -93,13 +94,32 @@ func (c urlChecker) resolveURL(u string, f string) (string, bool, error) {
 		return u, false, nil
 	}
 
+	// The file URLs are a mess. According to the RFC, they should be like
+	// file://host/absolute/path/to/file or file:///absolute/path/to/file
+	//
+	// But in real life, the following form is accepted:
+	// file://relative/path/to/file
+	//
+	// To handle this special case, we have to parse the URL by ourself
+	p := uu.Path
+	if uu.Scheme == "file" {
+		if !strings.HasPrefix(u, "file://") {
+			return "", false, fmt.Errorf("wrong file URL syntax")
+		}
+
+		p, err = url.PathUnescape(u[7:])
+		if err != nil {
+			return "", false, err
+		}
+	}
+
 	if !path.IsAbs(uu.Path) {
-		return path.Join(filepath.Dir(f), uu.Path), true, nil
+		return path.Join(filepath.Dir(f), p), true, nil
 	}
 
 	if c.documentRoot == "" {
 		return "", false, fmt.Errorf("document root directory is not specified")
 	}
 
-	return path.Join(c.documentRoot, uu.Path), true, nil
+	return path.Join(c.documentRoot, p), true, nil
 }
diff --git a/url_checker_test.go b/url_checker_test.go
index cc3e861..1cd4ea7 100644
--- a/url_checker_test.go
+++ b/url_checker_test.go
@@ -41,9 +41,12 @@ func TestURLCheckerCheckLocal(t *testing.T) {
 		assert.Equal(t, errSkipped, c.Check(u, "README.md"))
 	}
 
-	for _, u := range []string{"README.md"} {
+	for _, u := range []string{"README.md", "file://README.md"} {
 		assert.Equal(t, nil, c.Check(u, "README.md"))
 	}
+	for _, u := range []string{"file://foo-bar-missing-file-azertyuiop"} {
+		assert.NotEqual(t, nil, c.Check(u, "README.md"))
+	}
 }
 
 func TestURLCheckerCheckWithTimeout(t *testing.T) {