fix: make AddFixSuggestion thread-safe

internal/app/azldev/env.go

@@ -14,6 +14,7 @@ import (
 	"path/filepath"
 	"runtime"
 	"strings"
+	"sync"
 	"time"
 
 	"github.com/charmbracelet/gum/confirm"
@@ -92,13 +93,34 @@ type Env struct {
 
 	// Fix suggestion: a list of human readable hints that will be printed after an error to help the user
 	// resolve the issue. Printed in FIFO order.
-	fixSuggestions []string
+	fixSuggestions *fixSuggestionState
 
 	// lockStore provides cached access to per-component lock files.
 	// Nil when no project directory is configured.
 	lockStore *lockfile.Store
 }
 
+type fixSuggestionState struct {
+	mu          sync.Mutex
+	suggestions []string
+}
+
+// Add appends a fix suggestion in FIFO order.
+func (suggestions *fixSuggestionState) Add(suggestion string) {
+	suggestions.mu.Lock()
+	defer suggestions.mu.Unlock()
+
+	suggestions.suggestions = append(suggestions.suggestions, suggestion)
+}
+
+// All returns a copy of all collected fix suggestions.
+func (suggestions *fixSuggestionState) All() []string {
+	suggestions.mu.Lock()
+	defer suggestions.mu.Unlock()
+
+	return append([]string(nil), suggestions.suggestions...)
+}
+
 // Constructs a new [Env] using specified options.
 func NewEnv(ctx context.Context, options EnvOptions) *Env {
 	var workDir, logDir, outputDir string
@@ -150,7 +172,7 @@ func NewEnv(ctx context.Context, options EnvOptions) *Env {
 		constructionTime: time.Now(),
 
 		// No fix suggestions to start.
-		fixSuggestions: []string{},
+		fixSuggestions: &fixSuggestionState{},
 
 		// Lock store: created when we have a project directory.
 		lockStore: newLockStore(options.ProjectDir, options.Config, options.Interfaces.FileSystemFactory),
@@ -300,12 +322,14 @@ func (env *Env) OutputDir() string {
 // AddFixSuggestion records a human-readable hint that will be printed after an
 // error to help the user resolve the issue. Suggestions are printed in FIFO order.
 func (env *Env) AddFixSuggestion(suggestion string) {
-	env.fixSuggestions = append(env.fixSuggestions, suggestion)
+	env.fixSuggestions.Add(suggestion)
 }
 
 // PrintFixSuggestions prints the current fix suggestions, if any.
 func (env *Env) PrintFixSuggestions() {
-	if len(env.fixSuggestions) == 0 {
+	suggestions := env.fixSuggestions.All()
+
+	if len(suggestions) == 0 {
 		return
 	}
 
@@ -324,7 +348,7 @@ func (env *Env) PrintFixSuggestions() {
 	paddingSize := len(padding)
 
 	maxMsgLength := 0
-	for _, suggestion := range env.fixSuggestions {
+	for _, suggestion := range suggestions {
 		if len(suggestion) > maxMsgLength {
 			maxMsgLength = len(suggestion)
 		}
@@ -335,7 +359,7 @@ func (env *Env) PrintFixSuggestions() {
 
 	slog.Warn(boxEdgeString)
 
-	for _, suggestion := range env.fixSuggestions {
+	for _, suggestion := range suggestions {
 		slog.Warn(padding + suggestion)
 	}
 

internal/app/azldev/env_test.go

@@ -4,8 +4,12 @@
 package azldev_test
 
 import (
+	"bytes"
 	"context"
+	"fmt"
+	"log/slog"
 	"os"
+	"sync"
 	"testing"
 	"time"
 
@@ -16,6 +20,19 @@ import (
 	"github.com/stretchr/testify/require"
 )
 
+func setupTestLogger(logBuffer *bytes.Buffer) func() {
+	logger := slog.New(slog.NewTextHandler(logBuffer, &slog.HandlerOptions{
+		Level: slog.LevelDebug,
+	}))
+
+	previousDefaultLogger := slog.Default()
+	slog.SetDefault(logger)
+
+	return func() {
+		slog.SetDefault(previousDefaultLogger)
+	}
+}
+
 func TestNewEnv(t *testing.T) {
 	const (
 		testProjectRoot = "/non/existent/dir"
@@ -168,4 +185,69 @@ func TestFixSuggestions(t *testing.T) {
 			testEnv.Env.PrintFixSuggestions()
 		})
 	})
+
+	t.Run("suggestions added from child envs are visible on the parent env", func(t *testing.T) {
+		testEnv := testutils.NewTestEnv(t)
+
+		const suggestionCount = 32
+
+		var waitGroup sync.WaitGroup
+		for suggestionIndex := range suggestionCount {
+			waitGroup.Add(1)
+
+			go func(index int) {
+				defer waitGroup.Done()
+
+				childEnv, cancel := testEnv.Env.WithCancel()
+				defer cancel()
+
+				childEnv.AddFixSuggestion(fmt.Sprintf("child suggestion %d", index))
+			}(suggestionIndex)
+		}
+
+		waitGroup.Wait()
+
+		var logBuffer bytes.Buffer
+
+		restoreLogger := setupTestLogger(&logBuffer)
+		defer restoreLogger()
+
+		testEnv.Env.PrintFixSuggestions()
+
+		output := logBuffer.String()
+		for suggestionIndex := range suggestionCount {
+			assert.Contains(t, output, fmt.Sprintf("child suggestion %d", suggestionIndex))
+		}
+	})
+
+	t.Run("concurrent suggestions on the same env are all preserved", func(t *testing.T) {
+		testEnv := testutils.NewTestEnv(t)
+
+		const suggestionCount = 128
+
+		var waitGroup sync.WaitGroup
+		for suggestionIndex := range suggestionCount {
+			waitGroup.Add(1)
+
+			go func(index int) {
+				defer waitGroup.Done()
+
+				testEnv.Env.AddFixSuggestion(fmt.Sprintf("shared suggestion %d", index))
+			}(suggestionIndex)
+		}
+
+		waitGroup.Wait()
+
+		var logBuffer bytes.Buffer
+
+		restoreLogger := setupTestLogger(&logBuffer)
+		defer restoreLogger()
+
+		testEnv.Env.PrintFixSuggestions()
+
+		output := logBuffer.String()
+		for suggestionIndex := range suggestionCount {
+			assert.Contains(t, output, fmt.Sprintf("shared suggestion %d", suggestionIndex))
+		}
+	})
 }