fix: remove backwards compatibility for old experiment array format

mwbrooks · mwbrooks · commit c500bdeecb81 · 2026-03-17T10:21:41.000-07:00
Remove custom UnmarshalJSON methods and the unmarshalExperimentsField
helper that supported the deprecated array format for experiments in
config.json. The old format (["exp1"]) now produces a parse error with
a remediation hint to update to the object format ({"exp1": true}).
diff --git a/internal/config/experiments.go b/internal/config/experiments.go
@@ -25,6 +25,10 @@ import (
 	"github.com/slackapi/slack-cli/internal/slackerror"
 )
 
+// experimentsFormatHint is a remediation hint for config files that use the
+// deprecated array format for experiments instead of the current object format.
+const experimentsFormatHint = `If the "experiments" field is an array (e.g. ["exp1"]), update it to an object (e.g. {"exp1": true})`
+
 // LoadExperiments parses experiments from the command flags and configuration
 // files and stores the findings in Config
 func (c *Config) LoadExperiments(
diff --git a/internal/config/experiments_test.go b/internal/config/experiments_test.go
@@ -49,11 +49,11 @@ func Test_Config_WithExperimentOn(t *testing.T) {
 			fmt.Sprintf("active system experiments: [%s]", validExperiment))
 	})
 
-	t.Run("Correctly finds experiments from old array format in config.json", func(t *testing.T) {
+	t.Run("Returns a parse error with remediation for old array format in config.json", func(t *testing.T) {
 		// Setup
 		ctx, fs, _, config, pathToConfigJSON, teardown := setup(t)
 		defer teardown(t)
-		_, mockPrintDebug := setupMockPrintDebug()
+		mockOutput, mockPrintDebug := setupMockPrintDebug()
 
 		// Write old array format
 		jsonContents := []byte(
@@ -66,7 +66,8 @@ func Test_Config_WithExperimentOn(t *testing.T) {
 
 		config.LoadExperiments(ctx, mockPrintDebug)
 		experimentOn := config.WithExperimentOn(validExperiment)
-		assert.Equal(t, true, experimentOn)
+		assert.Equal(t, false, experimentOn)
+		assert.Contains(t, mockOutput.String(), "failed to parse system-level config file")
 	})
 
 	t.Run("Correctly returns false when experiments are not in config.json", func(t *testing.T) {
diff --git a/internal/config/experiments_unmarshal.go b/internal/config/experiments_unmarshal.go
diff --git a/internal/config/project.go b/internal/config/project.go
@@ -71,23 +71,6 @@ type ProjectConfig struct {
 	os types.Os
 }
 
-// UnmarshalJSON implements custom JSON unmarshaling for ProjectConfig to support
-// backwards compatibility with the old array format for experiments.
-func (c *ProjectConfig) UnmarshalJSON(data []byte) error {
-	type Alias ProjectConfig
-	aux := &struct {
-		RawExperiments json.RawMessage `json:"experiments,omitempty"`
-		*Alias
-	}{
-		Alias: (*Alias)(c),
-	}
-	if err := json.Unmarshal(data, aux); err != nil {
-		return err
-	}
-	c.Experiments = unmarshalExperimentsField(aux.RawExperiments)
-	return nil
-}
-
 // NewProjectConfig read and writes to the project-level configuration file
 func NewProjectConfig(fs afero.Fs, os types.Os) *ProjectConfig {
 	projectConfig := &ProjectConfig{
@@ -276,7 +259,11 @@ func ReadProjectConfigFile(ctx context.Context, fs afero.Fs, os types.Os) (Proje
 		return projectConfig, slackerror.New(slackerror.ErrUnableToParseJSON).
 			WithMessage("Failed to parse contents of project-level config file").
 			WithRootCause(err).
-			WithRemediation("Check that %s is valid JSON", style.HomePath(projectConfigFilePath))
+			WithRemediation(
+				"Check that %s is valid JSON. %s",
+				style.HomePath(projectConfigFilePath),
+				experimentsFormatHint,
+			)
 	}
 	if projectConfig.Surveys == nil {
 		projectConfig.Surveys = map[string]SurveyConfig{}
diff --git a/internal/config/system.go b/internal/config/system.go
@@ -81,25 +81,6 @@ type SystemConfig struct {
 	configFileLock sync.Mutex
 }
 
-// UnmarshalJSON implements custom JSON unmarshaling for SystemConfig to support
-// backwards compatibility with the old array format for experiments.
-// Old format: "experiments": ["charm", "sandboxes"]
-// New format: "experiments": {"charm": true, "sandboxes": true}
-func (c *SystemConfig) UnmarshalJSON(data []byte) error {
-	type Alias SystemConfig
-	aux := &struct {
-		RawExperiments json.RawMessage `json:"experiments,omitempty"`
-		*Alias
-	}{
-		Alias: (*Alias)(c),
-	}
-	if err := json.Unmarshal(data, aux); err != nil {
-		return err
-	}
-	c.Experiments = unmarshalExperimentsField(aux.RawExperiments)
-	return nil
-}
-
 // NewSystemConfig read and writes to the system-level configuration directory
 func NewSystemConfig(fs afero.Fs, os types.Os) *SystemConfig {
 	systemConfig := &SystemConfig{
@@ -151,7 +132,11 @@ func (c *SystemConfig) UserConfig(ctx context.Context) (*SystemConfig, error) {
 		return &config, slackerror.New(slackerror.ErrUnableToParseJSON).
 			WithMessage("Failed to parse contents of system-level config file").
 			WithRootCause(err).
-			WithRemediation("Check that %s is valid JSON", style.HomePath(path))
+			WithRemediation(
+				"Check that %s is valid JSON. %s",
+				style.HomePath(path),
+				experimentsFormatHint,
+			)
 	}
 
 	if config.Surveys == nil {
