fix: preserve zip headers for updated UTF-8 files

Author: ThomasK33

internal/aggregated/storage/storage_test.go

@@ -503,6 +503,18 @@ func TestTemplateStorageUpdatePreservesNonUTF8Files(t *testing.T) {
 		t.Fatal("expected non-UTF8 binary.dat to be omitted from spec.files")
 	}
 
+	originalSourceZip, ok := state.templateActiveSourceZip("acme", "starter-template")
+	if !ok {
+		t.Fatal("expected active source zip for starter-template before update")
+	}
+	mainModeBefore, ok := zipEntryMode(t, originalSourceZip, "main.tf")
+	if !ok {
+		t.Fatal("expected seeded source zip mode metadata for main.tf")
+	}
+	if mainModeBefore.Perm() != fs.FileMode(0o755) {
+		t.Fatalf("expected seeded main.tf mode 0755, got %v", mainModeBefore)
+	}
+
 	updatedMainTF := "resource \"null_resource\" \"updated_binary_preserve\" {}"
 	fileCountBefore := state.fileCount()
 	templateVersionCountBefore := state.templateVersionCount()
@@ -568,6 +580,14 @@ func TestTemplateStorageUpdatePreservesNonUTF8Files(t *testing.T) {
 		t.Fatalf("expected merged main.tf %q, got %q", updatedMainTF, string(updatedMainBytes))
 	}
 
+	updatedMainMode, ok := zipEntryMode(t, activeSourceZip, "main.tf")
+	if !ok {
+		t.Fatal("expected merged source zip mode metadata for main.tf")
+	}
+	if updatedMainMode.Perm() != fs.FileMode(0o755) {
+		t.Fatalf("expected preserved main.tf mode 0755, got %v", updatedMainMode)
+	}
+
 	expectedBinary := []byte{0x80, 0x81, 0x82}
 	binaryBytes, ok := zipEntries["binary.dat"]
 	if !ok {
@@ -2926,7 +2946,9 @@ func buildSeededTemplateSourceZip() ([]byte, error) {
 	var sourceZip bytes.Buffer
 	zipWriter := zip.NewWriter(&sourceZip)
 
-	mainTFWriter, err := zipWriter.Create("main.tf")
+	mainTFHeader := zip.FileHeader{Name: "main.tf", Method: zip.Deflate}
+	mainTFHeader.SetMode(fs.FileMode(0o755))
+	mainTFWriter, err := zipWriter.CreateHeader(&mainTFHeader)
 	if err != nil {
 		return nil, fmt.Errorf("create seeded main.tf zip entry: %w", err)
 	}

internal/aggregated/storage/template_files.go

@@ -212,6 +212,7 @@ func buildMergedSourceZip(originalZipBytes []byte, desiredFiles map[string]strin
 		header   zip.FileHeader
 	}
 	preservedBinaryFiles := make(map[string]preservedBinaryEntry)
+	originalHeaders := make(map[string]zip.FileHeader, len(archiveReader.File))
 	totalUncompressedBytes := int64(0)
 
 	for _, archiveFile := range archiveReader.File {
@@ -226,6 +227,12 @@ func buildMergedSourceZip(originalZipBytes []byte, desiredFiles map[string]strin
 		if err != nil {
 			return nil, fmt.Errorf("validate template source path %q: %w", archiveFile.Name, err)
 		}
+		if _, exists := originalHeaders[relativePath]; exists {
+			return nil, fmt.Errorf("duplicate normalized template source path %q", relativePath)
+		}
+		header := archiveFile.FileHeader
+		header.Name = relativePath
+		originalHeaders[relativePath] = header
 		if _, exists := normalizedDesiredFiles[relativePath]; exists {
 			continue
 		}
@@ -271,11 +278,9 @@ func buildMergedSourceZip(originalZipBytes []byte, desiredFiles map[string]strin
 			return nil, fmt.Errorf("duplicate normalized template source path %q", relativePath)
 		}
 
-		header := archiveFile.FileHeader
-		header.Name = relativePath
 		preservedBinaryFiles[relativePath] = preservedBinaryEntry{
 			contents: contents,
-			header:   header,
+			header:   originalHeaders[relativePath],
 		}
 	}
 
@@ -333,6 +338,26 @@ func buildMergedSourceZip(originalZipBytes []byte, desiredFiles map[string]strin
 		}
 
 		if hasDesired {
+			if originalHeader, exists := originalHeaders[sourcePath]; exists {
+				header := originalHeader
+				header.Name = sourcePath
+				// Header sizes are specific to the original contents. Reset them so
+				// the zip writer recomputes values for the updated file bytes.
+				header.CompressedSize64 = 0
+				header.UncompressedSize64 = 0
+				//nolint:staticcheck // archive/zip still consumes legacy 32-bit size fields.
+				header.CompressedSize = 0
+				//nolint:staticcheck // archive/zip still consumes legacy 32-bit size fields.
+				header.UncompressedSize = 0
+				fileWriter, err := zipWriter.CreateHeader(&header)
+				if err != nil {
+					return nil, fmt.Errorf("create zip entry %q from original header: %w", sourcePath, err)
+				}
+				if _, err := fileWriter.Write([]byte(desiredContent)); err != nil {
+					return nil, fmt.Errorf("write zip entry %q: %w", sourcePath, err)
+				}
+				continue
+			}
 			fileWriter, err := zipWriter.Create(sourcePath)
 			if err != nil {
 				return nil, fmt.Errorf("create zip entry %q: %w", sourcePath, err)