fix: address review feedback on typed errors

- Fix errors.go doc: clarify errors.As for classification, errors.Is for sentinels
- Preserve context in NotFound messages for parameter/return type validation
- Include full message in navigation profile NotFound error
- Use ValidationError for version parse failures instead of BackendError
- Include 'unsupported' prefix in container type UnsupportedError message

Author: retran

mdl/errors/errors.go

@@ -2,7 +2,9 @@
 
 // Package mdlerrors provides structured error types for the MDL executor.
 //
-// All error types support errors.Is and errors.As for programmatic classification.
+// Typed errors support errors.As for programmatic classification.
+// Sentinel or wrapped errors may also support errors.Is where applicable
+// (for example, ErrExit and BackendError via Unwrap).
 // Every error preserves the original message via Error() for backward-compatible
 // string output — callers that only use %v or .Error() see no change.
 //

mdl/executor/cmd_features.go

@@ -61,15 +61,15 @@ func (e *Executor) execShowFeatures(s *ast.ShowFeaturesStmt) error {
 		// SHOW FEATURES ADDED SINCE x.y
 		sinceV, err := versions.ParseSemVer(s.AddedSince)
 		if err != nil {
-			return mdlerrors.NewBackend("parse version "+s.AddedSince, err)
+			return mdlerrors.NewValidationf("invalid version %q: %v", s.AddedSince, err)
 		}
 		return e.showFeaturesAddedSince(reg, sinceV)
 
 	case s.ForVersion != "":
 		// SHOW FEATURES FOR VERSION x.y — no project connection needed
 		pv, err = versions.ParseSemVer(s.ForVersion)
 		if err != nil {
-			return mdlerrors.NewBackend("parse version "+s.ForVersion, err)
+			return mdlerrors.NewValidationf("invalid version %q: %v", s.ForVersion, err)
 		}
 
 	default:

mdl/executor/cmd_microflows_create.go

@@ -129,13 +129,15 @@ func (e *Executor) execCreateMicroflow(s *ast.CreateMicroflowStmt) error {
 		if p.Type.EntityRef != nil && !isBuiltinModuleEntity(p.Type.EntityRef.Module) {
 			entityID := entityResolver(*p.Type.EntityRef)
 			if entityID == "" {
-				return mdlerrors.NewNotFound("entity", p.Type.EntityRef.Module+"."+p.Type.EntityRef.Name)
+				return mdlerrors.NewNotFoundMsg("entity", p.Type.EntityRef.Module+"."+p.Type.EntityRef.Name,
+					fmt.Sprintf("entity '%s.%s' not found for parameter '%s'", p.Type.EntityRef.Module, p.Type.EntityRef.Name, p.Name))
 			}
 		}
 		// Validate enumeration references for Enumeration types
 		if p.Type.Kind == ast.TypeEnumeration && p.Type.EnumRef != nil {
 			if found := e.findEnumeration(p.Type.EnumRef.Module, p.Type.EnumRef.Name); found == nil {
-				return mdlerrors.NewNotFound("enumeration", p.Type.EnumRef.Module+"."+p.Type.EnumRef.Name)
+				return mdlerrors.NewNotFoundMsg("enumeration", p.Type.EnumRef.Module+"."+p.Type.EnumRef.Name,
+					fmt.Sprintf("enumeration '%s.%s' not found for parameter '%s'", p.Type.EnumRef.Module, p.Type.EnumRef.Name, p.Name))
 			}
 		}
 		param := &microflows.MicroflowParameter{
@@ -157,13 +159,15 @@ func (e *Executor) execCreateMicroflow(s *ast.CreateMicroflowStmt) error {
 		if s.ReturnType.Type.EntityRef != nil && !isBuiltinModuleEntity(s.ReturnType.Type.EntityRef.Module) {
 			entityID := entityResolver(*s.ReturnType.Type.EntityRef)
 			if entityID == "" {
-				return mdlerrors.NewNotFound("entity", s.ReturnType.Type.EntityRef.Module+"."+s.ReturnType.Type.EntityRef.Name)
+				return mdlerrors.NewNotFoundMsg("entity", s.ReturnType.Type.EntityRef.Module+"."+s.ReturnType.Type.EntityRef.Name,
+					fmt.Sprintf("entity '%s.%s' not found for return type", s.ReturnType.Type.EntityRef.Module, s.ReturnType.Type.EntityRef.Name))
 			}
 		}
 		// Validate enumeration references for return type
 		if s.ReturnType.Type.Kind == ast.TypeEnumeration && s.ReturnType.Type.EnumRef != nil {
 			if found := e.findEnumeration(s.ReturnType.Type.EnumRef.Module, s.ReturnType.Type.EnumRef.Name); found == nil {
-				return mdlerrors.NewNotFound("enumeration", s.ReturnType.Type.EnumRef.Module+"."+s.ReturnType.Type.EnumRef.Name)
+				return mdlerrors.NewNotFoundMsg("enumeration", s.ReturnType.Type.EnumRef.Module+"."+s.ReturnType.Type.EnumRef.Name,
+					fmt.Sprintf("enumeration '%s.%s' not found for return type", s.ReturnType.Type.EnumRef.Module, s.ReturnType.Type.EnumRef.Name))
 			}
 		}
 		mf.ReturnType = convertASTToMicroflowDataType(s.ReturnType.Type, entityResolver)

mdl/executor/cmd_navigation.go

@@ -33,7 +33,8 @@ func (e *Executor) execAlterNavigation(s *ast.AlterNavigationStmt) error {
 		}
 	}
 	if !profileFound {
-		return mdlerrors.NewNotFoundMsg("navigation profile", s.ProfileName, fmt.Sprintf("available: %s", profileNames(nav)))
+		return mdlerrors.NewNotFoundMsg("navigation profile", s.ProfileName,
+			fmt.Sprintf("navigation profile not found: %s (available: %s)", s.ProfileName, profileNames(nav)))
 	}
 
 	// Convert AST types to writer spec

mdl/executor/cmd_widgets.go

@@ -212,7 +212,7 @@ func (e *Executor) updateWidgetsInContainer(containerID string, widgetRefs []wid
 		return e.updateWidgetsInSnippet(containerID, containerName, widgetRefs, assignments, dryRun)
 	}
 
-	return 0, mdlerrors.NewUnsupported(fmt.Sprintf("container type: %s", containerType))
+	return 0, mdlerrors.NewUnsupported(fmt.Sprintf("unsupported container type: %s", containerType))
 }
 
 // updateWidgetsInPage updates widgets in a page using raw BSON.