WIP [ignore]: implement convention checker interface

BUILD.bazel

@@ -81,6 +81,7 @@ filegroup(
         "repository.rst",
         "//cmd:all_files",
         "//config:all_files",
+        "//convention:all_files",
         "//flag:all_files",
         "//internal:all_files",
         "//label:all_files",

README.rst

@@ -517,6 +517,14 @@ The following flags are accepted:
 | should use the index to resolve dependencies. If this is switched off, Gazelle would rely on               |
 | ``# gazelle:prefix`` directive or ``-go_prefix`` flag to resolve dependencies.                             |
 +-------------------------------------------------------------------+----------------------------------------+
+| :flag:`-use_conventions true|false`                               | :value:`false`                         |
++-------------------------------------------------------------------+----------------------------------------+
+| Usually used in combindation with `-index=false`, when enabled, this flag will check gazelle languages     |
+| for compliance with the `Convention` interface. Enabling the convention checker will add                   |
+| `# gazelle:resolve` directives to the root `BUILD.bazel` that do not follow the convention.                |
+| `CheckConvention(c *config.Config, kind, imp, name, rel string) bool` should be written to return false    |
+| for the a target and import path pair that do not follow the convention.                                   |
++-------------------------------------------------------------------+----------------------------------------+
 | :flag:`-go_grpc_compiler`                                         | ``@io_bazel_rules_go//proto:go_grpc``  |
 +-------------------------------------------------------------------+----------------------------------------+
 | The protocol buffers compiler to use for building go bindings for gRPC. May be repeated.                   |

cmd/gazelle/BUILD.bazel

@@ -25,6 +25,7 @@ go_library(
     visibility = ["//visibility:public"],
     deps = [
         "//config",
+        "//convention",
         "//flag",
         "//internal/wspace",
         "//label",

cmd/gazelle/fix-update.go

@@ -35,6 +35,7 @@ import (
 	"github.com/bazelbuild/bazel-gazelle/internal/wspace"
 	"github.com/bazelbuild/bazel-gazelle/label"
 	"github.com/bazelbuild/bazel-gazelle/language"
+	"github.com/bazelbuild/bazel-gazelle/convention"
 	"github.com/bazelbuild/bazel-gazelle/merger"
 	"github.com/bazelbuild/bazel-gazelle/repo"
 	"github.com/bazelbuild/bazel-gazelle/resolve"
@@ -55,6 +56,7 @@ type updateConfig struct {
 	patchBuffer    bytes.Buffer
 	print0         bool
 	profile        profiler
+	useConventions bool
 }
 
 type emitFunc func(c *config.Config, f *rule.File) error
@@ -90,6 +92,7 @@ func (ucr *updateConfigurer) RegisterFlags(fs *flag.FlagSet, cmd string, c *conf
 
 	fs.StringVar(&ucr.mode, "mode", "fix", "print: prints all of the updated BUILD files\n\tfix: rewrites all of the BUILD files in place\n\tdiff: computes the rewrite but then just does a diff")
 	fs.BoolVar(&ucr.recursive, "r", true, "when true, gazelle will update subdirectories recursively")
+	fs.BoolVar(&uc.useConventions, "use_conventions", false, "when true, gazelle will enable convention checking in fix-update.")
 	fs.StringVar(&uc.patchPath, "patch", "", "when set with -mode=diff, gazelle will write to a file instead of stdout")
 	fs.BoolVar(&uc.print0, "print0", false, "when set with -mode=fix, gazelle will print the names of rewritten files separated with \\0 (NULL)")
 	fs.StringVar(&ucr.cpuProfile, "cpuprofile", "", "write cpu profile to `file`")
@@ -263,7 +266,8 @@ func runFixUpdate(wd string, cmd command, args []string) (err error) {
 		&config.CommonConfigurer{},
 		&updateConfigurer{},
 		&walk.Configurer{},
-		&resolve.Configurer{})
+		&resolve.Configurer{},
+		&convention.Configurer{})
 
 	for _, lang := range languages {
 		cexts = append(cexts, lang)
@@ -313,6 +317,7 @@ func runFixUpdate(wd string, cmd command, args []string) (err error) {
 		}
 	}()
 
+	conventionChecker := convention.NewChecker(c, uc.dirs, mrslv.Resolver, exts...)
 	var errorsFromWalk []error
 	walk.Walk(c, cexts, uc.dirs, uc.walkMode, func(dir, rel string, c *config.Config, update bool, f *rule.File, subdirs, regularFiles, genFiles []string) {
 		// If this file is ignored or if Gazelle was not asked to update this
@@ -321,9 +326,14 @@ func runFixUpdate(wd string, cmd command, args []string) (err error) {
 			for _, repl := range c.KindMap {
 				mrslv.MappedKind(rel, repl)
 			}
-			if c.IndexLibraries && f != nil {
+			if f != nil {
 				for _, r := range f.Rules {
-					ruleIndex.AddRule(c, r, f)
+					if c.IndexLibraries {
+						ruleIndex.AddRule(c, r, f)
+					}
+					if uc.useConventions {
+						conventionChecker.AddRule(c, r, f)
+					}
 				}
 			}
 			return
@@ -448,10 +458,13 @@ func runFixUpdate(wd string, cmd command, args []string) (err error) {
 		})
 
 		// Add library rules to the dependency resolution table.
-		if c.IndexLibraries {
-			for _, r := range f.Rules {
+		for _, r := range f.Rules {
+			if c.IndexLibraries {
 				ruleIndex.AddRule(c, r, f)
 			}
+			if uc.useConventions {
+				conventionChecker.AddRule(c, r, f)
+			}
 		}
 	})
 
@@ -475,6 +488,9 @@ func runFixUpdate(wd string, cmd command, args []string) (err error) {
 	}
 
 	// Finish building the index for dependency resolution.
+	if uc.useConventions {
+		conventionChecker.Finish(c, ruleIndex)
+	}
 	ruleIndex.Finish()
 
 	// Resolve dependencies.

convention/BUILD.bazel

@@ -0,0 +1,55 @@
+load("@io_bazel_rules_go//go:def.bzl", "go_library", "go_test")
+
+go_library(
+    name = "convention",
+    srcs = [
+        "check.go",
+        "config.go",
+        "dir_set.go",
+    ],
+    importpath = "github.com/bazelbuild/bazel-gazelle/convention",
+    visibility = ["//visibility:public"],
+    deps = [
+        "//config",
+        "//label",
+        "//resolve",
+        "//rule",
+    ],
+)
+
+alias(
+    name = "go_default_library",
+    actual = ":convention",
+    visibility = ["//visibility:public"],
+)
+
+go_test(
+    name = "convention_test",
+    srcs = [
+        "check_test.go",
+        "config_test.go",
+    ],
+    embed = [":convention"],
+    deps = [
+        "//config",
+        "//label",
+        "//language/go",
+        "//language/proto",
+        "//resolve",
+        "//rule",
+    ],
+)
+
+filegroup(
+    name = "all_files",
+    testonly = True,
+    srcs = [
+        "BUILD.bazel",
+        "check.go",
+        "check_test.go",
+        "config.go",
+        "config_test.go",
+        "dir_set.go",
+    ],
+    visibility = ["//visibility:public"],
+)