Encorce filePath/FilePath casing in bufstyle

private/bufpkg/bufimage/image.go

@@ -31,11 +31,11 @@ func newImage(files []ImageFile, reorder bool) (*image, error) {
 		return nil, errors.New("image contains no files")
 	}
 	pathToImageFile := make(map[string]ImageFile, len(files))
-	type commitAndFilepath struct {
+	type commitAndFilePath struct {
 		commit   string
-		filepath string
+		filePath string
 	}
-	identityStringToCommitAndFilepath := make(map[string]commitAndFilepath)
+	identityStringToCommitAndFilePath := make(map[string]commitAndFilePath)
 	for _, file := range files {
 		path := file.Path()
 		if _, ok := pathToImageFile[path]; ok {
@@ -44,18 +44,18 @@ func newImage(files []ImageFile, reorder bool) (*image, error) {
 		pathToImageFile[path] = file
 		if moduleIdentity := file.ModuleIdentity(); moduleIdentity != nil {
 			identityString := moduleIdentity.IdentityString()
-			existing, ok := identityStringToCommitAndFilepath[identityString]
+			existing, ok := identityStringToCommitAndFilePath[identityString]
 			if ok {
 				if existing.commit != file.Commit() {
 					return nil, fmt.Errorf(
 						"files with different commits for the same module %s: %s:%s and %s:%s",
-						identityString, existing.filepath, existing.commit, path, file.Commit(),
+						identityString, existing.filePath, existing.commit, path, file.Commit(),
 					)
 				}
 			} else {
-				identityStringToCommitAndFilepath[identityString] = commitAndFilepath{
+				identityStringToCommitAndFilePath[identityString] = commitAndFilePath{
 					commit:   file.Commit(),
-					filepath: path,
+					filePath: path,
 				}
 			}
 		}

private/bufpkg/bufstyle/analyzers.go

@@ -92,5 +92,24 @@ func newAnalyzers() []*analysis.Analyzer {
 				return nil, nil
 			},
 		},
+		{
+			Name: "FILEPATH_CASING",
+			Doc:  "Verifies filePath or FilePath is used, not filepath or Filepath.",
+			Run: func(pass *analysis.Pass) (interface{}, error) {
+				if typesInfo := pass.TypesInfo; typesInfo != nil {
+					for _, object := range pass.TypesInfo.Defs {
+						if object != nil {
+							if strings.Contains(object.Name(), "Filepath") {
+								pass.Reportf(object.Pos(), `Use "FilePath" instead of "Filepath" in name %q`, object.Name())
+							}
+							if strings.Contains(object.Name(), "filepath") {
+								pass.Reportf(object.Pos(), `Use "filePath" instead of "filepath" in name %q`, object.Name())
+							}
+						}
+					}
+				}
+				return nil, nil
+			},
+		},
 	}
 }