config: accept PORT env + ensure colon (#1181)

* config: accept PORT env + ensure colon

* ensure precedence

config.dev.toml

@@ -71,8 +71,8 @@ StorageType = "memory"
 #TLSKeyFile = "server.key"
 
 # Port sets the port the proxy listens on
-# Env override: ATHENS_PORT
-# Note that PORT needs to be prefixed by :
+# Env override: ATHENS_PORT or PORT
+# The PORT must be a number or a number prefixed by ":"
 Port = ":3000"
 
 # The endpoint for a package registry in case of a proxy cache miss

pkg/config/config.go

@@ -160,12 +160,27 @@ func envOverride(config *Config) error {
 	if err != nil {
 		return err
 	}
+	portEnv := os.Getenv("PORT")
+	// ATHENS_PORT takes precedence over PORT
+	if portEnv != "" && os.Getenv("ATHENS_PORT") == "" {
+		config.Port = portEnv
+	}
 	if config.Port == "" {
 		config.Port = defaultPort
 	}
 	return nil
 }
 
+func ensurePortFormat(s string) string {
+	if len(s) == 0 {
+		return ""
+	}
+	if s[0] != ':' {
+		return ":" + s
+	}
+	return s
+}
+
 func validateConfig(config Config) error {
 	validate := validator.New()
 	err := validate.StructExcept(config, "Storage")

pkg/config/config_test.go

@@ -114,6 +114,34 @@ func TestEnvOverridesPreservingPort(t *testing.T) {
 	}
 }
 
+func TestEnvOverridesPORT(t *testing.T) {
+	conf := &Config{Port: ""}
+	oldVal := os.Getenv("PORT")
+	defer os.Setenv("PORT", oldVal)
+	os.Setenv("PORT", "5000")
+	err := envOverride(conf)
+	if err != nil {
+		t.Fatalf("Env override failed: %v", err)
+	}
+	if conf.Port != "5000" {
+		t.Fatalf("expected PORT env to be 5000 but got %v", conf.Port)
+	}
+}
+
+func TestEnsurePortFormat(t *testing.T) {
+	port := "3000"
+	expected := ":3000"
+	given := ensurePortFormat(port)
+	if given != expected {
+		t.Fatalf("expected ensurePortFormat to add a colon to %v but got %v", port, given)
+	}
+	port = ":3000"
+	given = ensurePortFormat(port)
+	if given != expected {
+		t.Fatalf("expected ensurePortFormat to not add a colon when it's present but got %v", given)
+	}
+}
+
 func TestStorageEnvOverrides(t *testing.T) {
 	expStorage := &StorageConfig{
 		Disk: &DiskConfig{