fix(diff+file): avoid filling defaults in config for kong

the previous logic was filling defaults in the configuration that was
passed to Kong. This was  problematic, especially where nils were
populated as defaults, e.g. if a shorthand_field was passed with some
value and the corresponding new field is auto-populated as `nil` by decK
, the auto-populated nil value would take precedence in Kong thus causing
the shorthand_field to be ignored
(https://konghq.atlassian.net/browse/KAG-5157).

This change applies the default values only to configurations used for
diff, the original configuration is always passed to Kong as is.

pkg/diff/diff.go

@@ -599,6 +599,36 @@ func (sc *Syncer) Solve(ctx context.Context, parallelism int, dry bool, isJSONOu
 		var err error
 		var result crud.Arg
 
+		// This variable holds the original event with the unchanged configuration
+		// Below the configuration in `e` may be modified. This is done solely for
+		// the purpose of displaying a correct diff and should not affect the
+		// configuration that is sent to Kong.
+		originalE := e
+
+		// If the event is for a plugin, inject defaults in the plugin's config
+		// that will be used for the diff. This is needed to avoid highlighting
+		// default values that were populated by Kong as differences.
+		if plugin, ok := e.Obj.(*state.Plugin); ok {
+			pluginCopy := &state.Plugin{
+				Plugin: *plugin.DeepCopy(),
+				Meta:   plugin.Meta,
+			}
+			e.Obj = pluginCopy
+
+			exists, err := utils.WorkspaceExists(ctx, sc.kongClient)
+			if err == nil && exists {
+				var schema map[string]interface{}
+				schema, err = sc.kongClient.Plugins.GetFullSchema(ctx, pluginCopy.Plugin.Name)
+				if err != nil {
+					return nil, err
+				}
+
+				if err := kong.FillPluginsDefaults(&pluginCopy.Plugin, schema); err != nil {
+					return nil, fmt.Errorf("failed filling plugin defaults: %w", err)
+				}
+			}
+		}
+
 		c := e.Obj.(state.ConsoleString)
 		objDiff := map[string]interface{}{
 			"old": e.OldObj,
@@ -680,7 +710,7 @@ func (sc *Syncer) Solve(ctx context.Context, parallelism int, dry bool, isJSONOu
 		if !dry {
 			// sync mode
 			// fire the request to Kong
-			result, err = sc.processor.Do(ctx, e.Kind, e.Op, e)
+			result, err = sc.processor.Do(ctx, originalE.Kind, originalE.Op, originalE)
 			// TODO https://github.com/Kong/go-database-reconciler/issues/22 this does not print, but is switched on
 			// sc.enableEntityActions because the existing behavior returns a result from the anon Run function.
 			// Refactoring should use only the channel and simplify the return, probably to just an error (all the other

pkg/file/builder.go

@@ -1443,44 +1443,6 @@ func (b *stateBuilder) ingestRoute(r FRoute) error {
 	return nil
 }
 
-func (b *stateBuilder) getPluginSchema(pluginName string) (map[string]interface{}, error) {
-	var schema map[string]interface{}
-
-	// lookup in cache
-	if schema, ok := b.schemasCache[pluginName]; ok {
-		return schema, nil
-	}
-
-	exists, err := utils.WorkspaceExists(b.ctx, b.client)
-	if err != nil {
-		return nil, fmt.Errorf("ensure workspace exists: %w", err)
-	}
-	if !exists {
-		return schema, ErrWorkspaceNotFound
-	}
-
-	schema, err = b.client.Plugins.GetFullSchema(b.ctx, &pluginName)
-	if err != nil {
-		return schema, err
-	}
-	b.schemasCache[pluginName] = schema
-	return schema, nil
-}
-
-func (b *stateBuilder) addPluginDefaults(plugin *FPlugin) error {
-	if b.client == nil {
-		return nil
-	}
-	schema, err := b.getPluginSchema(*plugin.Name)
-	if err != nil {
-		if errors.Is(err, ErrWorkspaceNotFound) {
-			return nil
-		}
-		return fmt.Errorf("retrieve schema for %v from Kong: %w", *plugin.Name, err)
-	}
-	return kong.FillPluginsDefaults(&plugin.Plugin, schema)
-}
-
 func (b *stateBuilder) ingestPlugins(plugins []FPlugin) error {
 	for _, p := range plugins {
 		p := p
@@ -1504,9 +1466,6 @@ func (b *stateBuilder) ingestPlugins(plugins []FPlugin) error {
 		if err != nil {
 			return err
 		}
-		if err := b.addPluginDefaults(&p); err != nil {
-			return fmt.Errorf("add defaults to plugin '%v': %w", *p.Name, err)
-		}
 		utils.MustMergeTags(&p, b.selectTags)
 		if plugin != nil {
 			p.Plugin.CreatedAt = plugin.CreatedAt