From 53a9db984e92a96e0ad8005434c68162446e2ed5 Mon Sep 17 00:00:00 2001
From: Raúl Benencia <id@rbenencia.name>
Date: Fri, 5 Jun 2026 16:21:18 -0300
Subject: Preserve empty flag values

---
 internal/environment/flags.go      | 37 +++++++++++----------
 internal/environment/flags_test.go | 67 ++++++++++++++++++++++++++++++++++++++
 2 files changed, 87 insertions(+), 17 deletions(-)

diff --git a/internal/environment/flags.go b/internal/environment/flags.go
index 2ffda31..dcb03fc 100644
--- a/internal/environment/flags.go
+++ b/internal/environment/flags.go
@@ -26,9 +26,9 @@ import (
 func (env *Environment) setFlags(args []string, environ []string) (*flag.FlagSet, error) {
 	env.setFlagDefaults()
 
-	configFile := configFileFromArgs(args)
-	if configFile == "" {
-		configFile = envValue(environ, "CONFIG")
+	configFile, configFromArgs := configFileFromArgs(args)
+	if !configFromArgs {
+		configFile, _ = envValue(environ, "CONFIG")
 	}
 	if configFile != "" {
 		env.ConfigFile = configFile
@@ -70,22 +70,22 @@ func (env *Environment) registerFlags() *flag.FlagSet {
 	return flags
 }
 
-func configFileFromArgs(args []string) string {
+func configFileFromArgs(args []string) (string, bool) {
 	for i, arg := range args {
 		if arg == "-config" || arg == "--config" {
 			if i+1 < len(args) {
-				return args[i+1]
+				return args[i+1], true
 			}
-			return ""
+			return "", true
 		}
 		if strings.HasPrefix(arg, "-config=") {
-			return strings.TrimPrefix(arg, "-config=")
+			return strings.TrimPrefix(arg, "-config="), true
 		}
 		if strings.HasPrefix(arg, "--config=") {
-			return strings.TrimPrefix(arg, "--config=")
+			return strings.TrimPrefix(arg, "--config="), true
 		}
 	}
-	return ""
+	return "", false
 }
 
 func (env *Environment) loadConfigFile(configFile string) error {
@@ -155,24 +155,27 @@ func (env *Environment) applyEnvVars(environ []string) error {
 }
 
 func (env *Environment) applyEnvVar(environ []string, key, name string) error {
-	return env.setConfigValue(key, envValue(environ, name))
+	value, ok := envValue(environ, name)
+	if !ok {
+		return nil
+	}
+	if key == "debug" && value == "" {
+		value = "true"
+	}
+	return env.setConfigValue(key, value)
 }
 
-func envValue(environ []string, name string) string {
+func envValue(environ []string, name string) (string, bool) {
 	for _, entry := range environ {
 		key, value, found := strings.Cut(entry, "=")
 		if found && key == name {
-			return value
+			return value, true
 		}
 	}
-	return ""
+	return "", false
 }
 
 func (env *Environment) setConfigValue(key, value string) error {
-	if value == "" {
-		return nil
-	}
-
 	switch key {
 	case "config":
 		env.ConfigFile = value
diff --git a/internal/environment/flags_test.go b/internal/environment/flags_test.go
index 2c2750d..782a336 100644
--- a/internal/environment/flags_test.go
+++ b/internal/environment/flags_test.go
@@ -101,6 +101,72 @@ func TestSetFlagsCLIConfigOverridesEnvConfig(t *testing.T) {
 	}
 }
 
+func TestSetFlagsEmptyEnvOverridesConfigValue(t *testing.T) {
+	configFile := writeConfig(t, "shoelaces.conf", "base-url=config-base-url\n")
+
+	env := defaultEnvironment()
+	if _, err := env.setFlags(nil, []string{"CONFIG=" + configFile, "BASE_URL="}); err != nil {
+		t.Fatal(err)
+	}
+
+	if env.BaseURL != "" {
+		t.Errorf("Expected empty base URL from env, got %q", env.BaseURL)
+	}
+}
+
+func TestSetFlagsEmptyEnvOverridesDefaultValue(t *testing.T) {
+	env := defaultEnvironment()
+	if _, err := env.setFlags(nil, []string{"ENV_DIR="}); err != nil {
+		t.Fatal(err)
+	}
+
+	if env.EnvDir != "" {
+		t.Errorf("Expected empty env dir from env, got %q", env.EnvDir)
+	}
+}
+
+func TestSetFlagsEmptyConfigValueOverridesDefault(t *testing.T) {
+	configFile := writeConfig(t, "shoelaces.conf", "env-dir=\n")
+
+	env := defaultEnvironment()
+	if _, err := env.setFlags([]string{"-config", configFile}, nil); err != nil {
+		t.Fatal(err)
+	}
+
+	if env.EnvDir != "" {
+		t.Errorf("Expected empty env dir from config, got %q", env.EnvDir)
+	}
+}
+
+func TestSetFlagsEmptyCLIConfigSkipsEnvConfig(t *testing.T) {
+	envConfig := writeConfig(t, "env.conf", "base-url=env-config-base-url\n")
+
+	env := defaultEnvironment()
+	if _, err := env.setFlags([]string{"-config="}, []string{"CONFIG=" + envConfig}); err != nil {
+		t.Fatal(err)
+	}
+
+	if env.BaseURL != "" {
+		t.Errorf("Expected env config file to be skipped, got base URL %q", env.BaseURL)
+	}
+	if env.ConfigFile != "" {
+		t.Errorf("Expected empty config file from CLI, got %q", env.ConfigFile)
+	}
+}
+
+func TestSetFlagsEmptyBoolEnvMeansTrue(t *testing.T) {
+	configFile := writeConfig(t, "shoelaces.conf", "debug=false\n")
+
+	env := defaultEnvironment()
+	if _, err := env.setFlags(nil, []string{"CONFIG=" + configFile, "DEBUG="}); err != nil {
+		t.Fatal(err)
+	}
+
+	if !env.Debug {
+		t.Error("Expected empty DEBUG env var to set debug true")
+	}
+}
+
 func TestSetFlagsReturnsConfigErrors(t *testing.T) {
 	tests := []struct {
 		name   string
@@ -108,6 +174,7 @@ func TestSetFlagsReturnsConfigErrors(t *testing.T) {
 	}{
 		{name: "unknown key", config: "unknown=value\n"},
 		{name: "invalid bool", config: "debug=maybe\n"},
+		{name: "empty bool", config: "debug=\n"},
 	}
 
 	for _, tt := range tests {
-- 
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