Merge pull request #48 from johnweldon/45-migration-file-id-clash

Proposed fix for migration file name clashes

file/file.go

@@ -163,9 +163,18 @@ func ReadMigrationFiles(path string, filenameRegex *regexp.Regexp) (files Migrat
 		d        direction.Direction
 	}
 	tmpFiles := make([]*tmpFile, 0)
+	tmpFileMap := map[uint64]map[direction.Direction]tmpFile{}
 	for _, file := range ioFiles {
 		version, name, d, err := parseFilenameSchema(file.Name(), filenameRegex)
 		if err == nil {
+			if _, ok := tmpFileMap[version]; !ok {
+				tmpFileMap[version] = map[direction.Direction]tmpFile{}
+			}
+			if existing, ok := tmpFileMap[version][d]; !ok {
+				tmpFileMap[version][d] = tmpFile{version: version, name: name, filename: file.Name(), d: d}
+			} else {
+				return nil, fmt.Errorf("duplicate migration file version %d : %q and %q", version, existing.filename, file.Name())
+			}
 			tmpFiles = append(tmpFiles, &tmpFile{version, name, file.Name(), d})
 		}
 	}

file/file_test.go

@@ -209,3 +209,45 @@ func TestFiles(t *testing.T) {
 	}
 
 }
+
+func TestDuplicateFiles(t *testing.T) {
+	dups := []string{
+		"001_migration.up.sql",
+		"001_duplicate.up.sql",
+	}
+
+	root, cleanFn, err := makeFiles("TestDuplicateFiles", dups...)
+	defer cleanFn()
+
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	_, err = ReadMigrationFiles(root, FilenameRegex("sql"))
+	if err == nil {
+		t.Fatal("Expected duplicate migration file error")
+	}
+}
+
+// makeFiles takes an identifier, and a list of file names and uses them to create a temporary
+// directory populated with files named with the names passed in.  makeFiles returns the root
+// directory name, and a func suitable for a defer cleanup to remove the temporary files after
+// the calling function exits.
+func makeFiles(testname string, names ...string) (root string, cleanup func(), err error) {
+	cleanup = func() {}
+	root, err = ioutil.TempDir("/tmp", testname)
+	if err != nil {
+		return
+	}
+	cleanup = func() { os.RemoveAll(root) }
+	if err = ioutil.WriteFile(path.Join(root, "nonsense.txt"), nil, 0755); err != nil {
+		return
+	}
+
+	for _, name := range names {
+		if err = ioutil.WriteFile(path.Join(root, name), nil, 0755); err != nil {
+			return
+		}
+	}
+	return
+}