From f30d72f66d6b59414004063a164e4ca5f9ac3b2a Mon Sep 17 00:00:00 2001
From: Julian Friedman <github@julianfriedman.org>
Date: Mon, 28 Aug 2023 15:58:09 +0100
Subject: [PATCH] Use Compile method in preference to mutex

This also means we no longer expose the rules field publicly, which
seems better.
---
 analyzer.go |  7 ++++---
 config.go   | 47 ++++++++++++++++++++++-------------------------
 2 files changed, 26 insertions(+), 28 deletions(-)

diff --git a/analyzer.go b/analyzer.go
index a1272b9..893e42b 100644
--- a/analyzer.go
+++ b/analyzer.go
@@ -31,19 +31,20 @@ func run(pass *analysis.Pass) (interface{}, error) {
 }
 
 func runWithConfig(config *Config, pass *analysis.Pass) (interface{}, error) {
-	if err := config.CompileRegexp(); err != nil {
+	c, err := config.Compile()
+	if err != nil {
 		return nil, err
 	}
 
 	inspect := pass.ResultOf[inspect.Analyzer].(*inspector.Inspector)
 	inspect.Preorder([]ast.Node{(*ast.ImportSpec)(nil)}, func(n ast.Node) {
-		visitImportSpecNode(config, n.(*ast.ImportSpec), pass)
+		visitImportSpecNode(c, n.(*ast.ImportSpec), pass)
 	})
 
 	return nil, nil
 }
 
-func visitImportSpecNode(config *Config, node *ast.ImportSpec, pass *analysis.Pass) {
+func visitImportSpecNode(config *CompiledConfig, node *ast.ImportSpec, pass *analysis.Pass) {
 	if !config.DisallowUnaliased && node.Name == nil {
 		return
 	}
diff --git a/config.go b/config.go
index 6c16a99..d1cb653 100644
--- a/config.go
+++ b/config.go
@@ -4,28 +4,25 @@ import (
 	"errors"
 	"fmt"
 	"regexp"
-	"sync"
 )
 
 type Config struct {
 	RequiredAlias        map[string]string
-	Rules                []*Rule
 	DisallowUnaliased    bool
 	DisallowExtraAliases bool
-	muRules              sync.Mutex
 }
 
-func (c *Config) CompileRegexp() error {
-	c.muRules.Lock()
-	defer c.muRules.Unlock()
-	if c.Rules != nil {
-		return nil
-	}
+type CompiledConfig struct {
+	Config
+	rules []*Rule
+}
+
+func (c Config) Compile() (*CompiledConfig, error) {
 	rules := make([]*Rule, 0, len(c.RequiredAlias))
 	for path, alias := range c.RequiredAlias {
 		reg, err := regexp.Compile(fmt.Sprintf("^%s$", path))
 		if err != nil {
-			return err
+			return nil, err
 		}
 
 		rules = append(rules, &Rule{
@@ -33,24 +30,14 @@ func (c *Config) CompileRegexp() error {
 			Alias:  alias,
 		})
 	}
-	c.Rules = rules
-	return nil
-}
-
-func (c *Config) findRule(path string) *Rule {
-	c.muRules.Lock()
-	rules := c.Rules
-	c.muRules.Unlock()
-	for _, rule := range rules {
-		if rule.Regexp.MatchString(path) {
-			return rule
-		}
-	}
 
-	return nil
+	return &CompiledConfig{
+		Config: c,
+		rules:  rules,
+	}, nil
 }
 
-func (c *Config) AliasFor(path string) (string, bool) {
+func (c *CompiledConfig) AliasFor(path string) (string, bool) {
 	rule := c.findRule(path)
 	if rule == nil {
 		return "", false
@@ -64,6 +51,16 @@ func (c *Config) AliasFor(path string) (string, bool) {
 	return alias, true
 }
 
+func (c *CompiledConfig) findRule(path string) *Rule {
+	for _, rule := range c.rules {
+		if rule.Regexp.MatchString(path) {
+			return rule
+		}
+	}
+
+	return nil
+}
+
 type Rule struct {
 	Alias  string
 	Regexp *regexp.Regexp