fix: address timing issue with .env file watcher (#16)

Author: kyubisation

serve/config/dotenv.go

@@ -25,8 +25,9 @@ func CreateDotEnv(workingDirectory string, onChange func(variables map[string]*s
 		slog.Info(fmt.Sprintf("Detected .env file at %v. Reading variables and adding watch.", configEnvPath))
 		env = parseDotEnv(configEnvPath)
 	} else {
-		slog.Info(fmt.Sprintf("Detected .env file at %v. Reading variables.", configEnvPath))
-		env = parseDotEnv(filepath.Join(workingDirectory, ".env"))
+		localEnv := filepath.Join(workingDirectory, ".env")
+		slog.Info(fmt.Sprintf("Detected .env file at %v. Reading variables.", localEnv))
+		env = parseDotEnv(localEnv)
 	}
 
 	instance := DotEnv{

serve/config/filewatcher.go

@@ -3,6 +3,7 @@ package config
 import (
 	"log/slog"
 	"path"
+	"time"
 
 	"github.com/fsnotify/fsnotify"
 )
@@ -44,6 +45,12 @@ func CreateFileWatcher() *FileWatcher {
 					if ok {
 						for _, watchable := range watchables {
 							if watchable.Name() == name {
+								// When e.g. using os.WriteFile, the truncation already triggers
+								// a change event, which results in the file being empty when
+								// calling HandleChange.
+								// Due to this, we wait for a millisecond, which should be enough for
+								// the write operation to finish.
+								time.Sleep(time.Millisecond)
 								watchable.HandleChange()
 							}
 							return

serve/config/filewatcher_test.go

@@ -33,23 +33,12 @@ func TestShouldUpdateDotEnvOnChange(t *testing.T) {
 
 	test.AssertEqual(t, len(testEnv.env), 3)
 
-	f, err := os.OpenFile(envFilePath, os.O_WRONLY, 0666)
+	err = os.WriteFile(envFilePath, []byte("TEST = example"), 0666)
 	if err != nil {
 		t.Fatalf("failed to write to file: %s", err)
 	}
 
-	f.Sync()
-	time.Sleep(time.Millisecond)
-	f.WriteString("TEST = example")
-	f.Sync()
-	f.Close()
-
-	// This test is flaky on GitHub Actions, so we do this workaround
-	counter := 0
-	for counter < 200 && len(testEnv.env) != 1 {
-		time.Sleep(time.Millisecond * 50)
-		counter++
-	}
+	time.Sleep(time.Millisecond * 50)
 
 	test.AssertEqual(t, len(testEnv.env), 1)
 	test.AssertEqual(t, readValue(t, testEnv.env, "TEST"), "example")