Add -strict to exit on build file and directive errors

.bazelci/presubmit.yml

@@ -38,3 +38,4 @@ platforms:
     # gazelle prints file paths with backward slashes on windows,
     # which doesn't match the golden files generated on *nix.
     - "-//tests:fix_mode_print0"
+    - "-//tests:fix_mode_strict"

config/config.go

@@ -77,6 +77,10 @@ type Config struct {
 	// usage of deprecated rules.
 	ShouldFix bool
 
+	// Strict determines how Gazelle handles build file and directive errors. When
+	// set, Gazelle will exit with non-zero value after logging such errors.
+	Strict bool
+
 	// IndexLibraries determines whether Gazelle should build an index of
 	// libraries in the workspace for dependency resolution
 	IndexLibraries bool
@@ -186,14 +190,15 @@ type Configurer interface {
 // i.e., those that apply to Config itself and not to Config.Exts.
 type CommonConfigurer struct {
 	repoRoot, buildFileNames, readBuildFilesDir, writeBuildFilesDir string
-	indexLibraries                                                  bool
+	indexLibraries, strict                                          bool
 	langCsv                                                         string
 }
 
 func (cc *CommonConfigurer) RegisterFlags(fs *flag.FlagSet, cmd string, c *Config) {
 	fs.StringVar(&cc.repoRoot, "repo_root", "", "path to a directory which corresponds to go_prefix, otherwise gazelle searches for it.")
 	fs.StringVar(&cc.buildFileNames, "build_file_name", strings.Join(DefaultValidBuildFileNames, ","), "comma-separated list of valid build file names.\nThe first element of the list is the name of output build files to generate.")
 	fs.BoolVar(&cc.indexLibraries, "index", true, "when true, gazelle will build an index of libraries in the workspace for dependency resolution")
+	fs.BoolVar(&cc.strict, "strict", false, "when true, gazelle will exit with none-zero value for build file syntax errors or unknown directives")
 	fs.StringVar(&cc.readBuildFilesDir, "experimental_read_build_files_dir", "", "path to a directory where build files should be read from (instead of -repo_root)")
 	fs.StringVar(&cc.writeBuildFilesDir, "experimental_write_build_files_dir", "", "path to a directory where build files should be written to (instead of -repo_root)")
 	fs.StringVar(&cc.langCsv, "lang", "", "if non-empty, process only these languages (e.g. \"go,proto\")")
@@ -235,6 +240,7 @@ func (cc *CommonConfigurer) CheckFlags(fs *flag.FlagSet, c *Config) error {
 		}
 	}
 	c.IndexLibraries = cc.indexLibraries
+	c.Strict = cc.strict
 	if len(cc.langCsv) > 0 {
 		c.Langs = strings.Split(cc.langCsv, ",")
 	}

tests/fix_mode_strict/BUILD.in

@@ -0,0 +1,4 @@
+go_library(
+  name = "syntax_error_no_comma"
+  visibility = ["//visibility:public"],
+)

tests/fix_mode_strict/BUILD.out

@@ -0,0 +1,4 @@
+go_library(
+  name = "syntax_error_no_comma"
+  visibility = ["//visibility:public"],
+)

tests/fix_mode_strict/README.md

@@ -0,0 +1,4 @@
+# Gazelle fix -strict mode
+
+When Gazelle is run with the `-strict` flag, it will exit with none-zero value
+for build file syntax errors or unknown directives.

tests/fix_mode_strict/arguments.txt

@@ -0,0 +1 @@
+-strict

tests/fix_mode_strict/expectedExitCode.txt

@@ -0,0 +1 @@
+1

tests/fix_mode_strict/expectedStderr.txt

@@ -0,0 +1,2 @@
+gazelle: %WORKSPACEPATH%/BUILD.bazel:3:13: syntax error near visibility
+gazelle: Exit as strict mode is on

walk/walk.go

@@ -136,6 +136,11 @@ func Walk(c *config.Config, cexts []config.Configurer, dirs []string, mode Mode,
 		f, err := loadBuildFile(c, rel, dir, files)
 		if err != nil {
 			log.Print(err)
+			if c.Strict {
+				// TODO(https://github.com/bazelbuild/bazel-gazelle/issues/1029):
+				// Refactor to accumulate and propagate errors to main.
+				log.Fatal("Exit as strict mode is on")
+			}
 			haveError = true
 		}
 
@@ -275,6 +280,11 @@ func configure(cexts []config.Configurer, knownDirectives map[string]bool, c *co
 		for _, d := range f.Directives {
 			if !knownDirectives[d.Key] {
 				log.Printf("%s: unknown directive: gazelle:%s", f.Path, d.Key)
+				if c.Strict {
+					// TODO(https://github.com/bazelbuild/bazel-gazelle/issues/1029):
+					// Refactor to accumulate and propagate errors to main.
+					log.Fatal("Exit as strict mode is on")
+				}
 			}
 		}
 	}