fix: Modify isCoverPage check conditions (#10453)

fix: modify isCoverPage check conditions

Author: filzrev

samples/seed/docfx.json

@@ -70,7 +70,7 @@
       { "files": [ "**" ], "src": "obj/md", "dest": "md" },
       { "files": [ "**" ], "src": "obj/apipage", "dest": "apipage" },
       { "files": [ "articles/**/*.{md,yml}", "*.md", "toc.yml", "restapi/**" ] },
-      { "files": [ "pdf/**" ] }
+      { "files": [ "pdf/*.{md,yml}" ] }
     ],
     "resource": [
       {

src/Docfx.App/PdfBuilder.cs

@@ -106,7 +106,7 @@ await Parallel.ForEachAsync(pdfTocs, async (item, _) =>
                 var outputPath = Path.Combine(outputFolder, outputName);
 
                 await CreatePdf(
-                    PrintPdf, PrintHeaderFooter, task, new(baseUrl, url), toc, outputPath,
+                    PrintPdf, PrintHeaderFooter, task, new(baseUrl, url), toc, outputFolder, outputPath,
                     pageNumbers => pdfPageNumbers[url] = pageNumbers);
 
                 task.Value = task.MaxValue;
@@ -256,7 +256,7 @@ static string ExpandTemplate(string? pdfTemplate, int pageNumber, int totalPages
 
     static async Task CreatePdf(
         Func<Outline, Uri, Task<byte[]?>> printPdf, Func<Outline, int, int, Page, Task<byte[]>> printHeaderFooter, ProgressTask task,
-        Uri outlineUrl, Outline outline, string outputPath, Action<Dictionary<Outline, int>> updatePageNumbers)
+        Uri outlineUrl, Outline outline, string outputFolder, string outputPath, Action<Dictionary<Outline, int>> updatePageNumbers)
     {
         var tempDirectory = Path.Combine(Path.GetTempPath(), ".docfx", "pdf", "pages");
         Directory.CreateDirectory(tempDirectory);
@@ -357,7 +357,7 @@ async Task MergePdf()
                 if (!pageBytes.TryGetValue(node, out var bytes))
                     continue;
 
-                var isCoverPage = url.AbsolutePath.TrimStart('/').Equals(outline.pdfCoverPage, GetStringComparison());
+                var isCoverPage = IsCoverPage(url, outputFolder, outline.pdfCoverPage);
 
                 var isTocPage = IsTocPage(url);
                 if (isTocPage)
@@ -440,6 +440,19 @@ PdfAction HandleUriAction(UriAction url)
 
         static Uri CleanUrl(Uri url) => new UriBuilder(url) { Query = null, Fragment = null }.Uri;
 
+        static bool IsCoverPage(Uri pageUri, string baseFolder, string? pdfCoverPage)
+        {
+            Debug.Assert(Path.IsPathFullyQualified(baseFolder));
+
+            if (string.IsNullOrEmpty(pdfCoverPage))
+                return false;
+
+            string pagePath = pageUri.AbsolutePath.TrimStart('/');
+            string covePagePath = PathUtility.MakeRelativePath(baseFolder, Path.GetFullPath(Path.Combine(baseFolder, pdfCoverPage)));
+
+            return pagePath.Equals(covePagePath, GetStringComparison());
+        }
+
         static bool IsTocPage(Uri url) => url.AbsolutePath.StartsWith("/_pdftoc/");
 
         Bookmarks CreateBookmarks(Outline[]? items)