Flag replacement for custom recipes

playground/cmd_validate.go

@@ -95,6 +95,10 @@ func validateYAMLRecipe(recipe *YAMLRecipe, baseRecipes []Recipe, result *Valida
 					if serviceConfig.Remove {
 						result.AddWarning("removing service '%s' from component '%s' - verify names match base recipe", serviceName, componentName)
 					}
+					// Validate args and replace_args are mutually exclusive
+					if len(serviceConfig.Args) > 0 && len(serviceConfig.ReplaceArgs) > 0 {
+						result.AddError("service '%s' in component '%s': args and replace_args cannot be used together", serviceName, componentName)
+					}
 				}
 			}
 		}

playground/recipe_yaml.go

@@ -49,9 +49,14 @@ type YAMLServiceConfig struct {
 	// Entrypoint overrides the container entrypoint
 	Entrypoint string `yaml:"entrypoint,omitempty"`
 
-	// Args are the arguments to pass to the service
+	// Args are the arguments to pass to the service.
+	// This should be used when ReplaceArgs is not used.
 	Args []string `yaml:"args,omitempty"`
 
+	// ReplaceArgs are the arguments to replace in the service.
+	// This should be used when Args is not used.
+	ReplaceArgs []string `yaml:"replace_args,omitempty"`
+
 	// Env is a map of environment variables
 	Env map[string]string `yaml:"env,omitempty"`
 
@@ -432,6 +437,9 @@ func applyServiceOverrides(svc *Service, config *YAMLServiceConfig, root *Compon
 	if len(config.Args) > 0 {
 		svc.Args = config.Args
 	}
+	if len(config.ReplaceArgs) > 0 {
+		svc.Args = applyReplaceArgs(svc.Args, config.ReplaceArgs)
+	}
 	if config.Env != nil {
 		if svc.Env == nil {
 			svc.Env = make(map[string]string)
@@ -470,6 +478,39 @@ func applyServiceOverrides(svc *Service, config *YAMLServiceConfig, root *Compon
 	}
 }
 
+// applyReplaceArgs replaces arguments in the existing args list.
+// ReplaceArgs contains flag-value pairs in sequence: ["--flag", "new-value", "--other-flag", "other-value"]
+// For each pair, it finds the flag in args and replaces its following value.
+func applyReplaceArgs(args, replaceArgs []string) []string {
+	if len(replaceArgs)%2 != 0 {
+		slog.Warn("replace_args should contain pairs of flag and value", "count", len(replaceArgs))
+	}
+
+	result := make([]string, len(args))
+	copy(result, args)
+
+	for i := 0; i < len(replaceArgs); i += 2 {
+		flag := replaceArgs[i]
+		newValue := replaceArgs[i+1]
+		result = applyReplacePair(flag, newValue, result)
+	}
+
+	return result
+}
+
+// applyReplacePair finds flag in args and replaces the following value with newValue.
+func applyReplacePair(flag, newValue string, args []string) []string {
+	for i := 0; i < len(args); i++ {
+		if args[i] == flag && i+1 < len(args) {
+			args[i+1] = newValue
+			return args
+		}
+	}
+
+	slog.Warn("replace_args flag not found in service args", "flag", flag)
+	return args
+}
+
 // yamlReleaseToRelease converts a YAMLReleaseConfig to a release struct
 func yamlReleaseToRelease(cfg *YAMLReleaseConfig) *release {
 	return &release{

playground/recipe_yaml_test.go

@@ -830,3 +830,57 @@ func TestApplyDependsOn_UnknownCondition(t *testing.T) {
 	require.Equal(t, "db", svc.DependsOn[0].Name)
 	require.Equal(t, DependsOnConditionHealthy, svc.DependsOn[0].Condition)
 }
+
+func TestApplyServiceOverrides_WithReplaceArgs(t *testing.T) {
+	tests := []struct {
+		name        string
+		args        []string
+		replaceArgs []string
+		expected    []string
+	}{
+		{
+			name:        "replace single pair",
+			args:        []string{"--port", "8080", "--host", "localhost"},
+			replaceArgs: []string{"--port", "9090"},
+			expected:    []string{"--port", "9090", "--host", "localhost"},
+		},
+		{
+			name:        "replace multiple pairs",
+			args:        []string{"--port", "8080", "--host", "localhost", "--timeout", "30"},
+			replaceArgs: []string{"--port", "9090", "--timeout", "60"},
+			expected:    []string{"--port", "9090", "--host", "localhost", "--timeout", "60"},
+		},
+		{
+			name:        "replace with subcommand present",
+			args:        []string{"node", "--datadir", "/old", "--port", "8080"},
+			replaceArgs: []string{"--datadir", "/new", "--port", "9090"},
+			expected:    []string{"node", "--datadir", "/new", "--port", "9090"},
+		},
+		{
+			name:        "replace last flag",
+			args:        []string{"--first", "value1", "--second", "value2"},
+			replaceArgs: []string{"--second", "newvalue2"},
+			expected:    []string{"--first", "value1", "--second", "newvalue2"},
+		},
+		{
+			name:        "empty replace args",
+			args:        []string{"--port", "8080"},
+			replaceArgs: []string{},
+			expected:    []string{"--port", "8080"},
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			svc := &Service{
+				Name: "test-svc",
+				Args: tt.args,
+			}
+			config := &YAMLServiceConfig{
+				ReplaceArgs: tt.replaceArgs,
+			}
+			applyServiceOverrides(svc, config, nil)
+			require.Equal(t, tt.expected, svc.Args)
+		})
+	}
+}