feat: add CREATE/DROP CONFIGURATION and DROP constant override

Add three new commands for configuration management:
- CREATE CONFIGURATION 'Name' [Key = Value, ...] — new server config
- DROP CONFIGURATION 'Name' — remove a server configuration
- ALTER SETTINGS DROP CONSTANT 'Name' IN CONFIGURATION 'cfg' — remove
  a constant override (reset to default value)

Full pipeline: grammar → parser → AST → visitor → executor.
Updated help topics, quick reference, language reference, site docs,
and skills.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: ako

.claude/skills/mendix/project-settings.md

@@ -67,6 +67,25 @@ ALTER SETTINGS CONSTANT 'BusinessEvents.ServerUrl' VALUE 'kafka:9092'
 
 -- Without IN CONFIGURATION (uses first configuration)
 ALTER SETTINGS CONSTANT 'MyModule.ApiKey' VALUE 'abc123';
+
+-- Remove a constant override (reset to default)
+ALTER SETTINGS DROP CONSTANT 'MyModule.ApiKey' IN CONFIGURATION 'Default';
+```
+
+### Create / Drop Configurations
+
+```sql
+-- Create a new server configuration
+CREATE CONFIGURATION 'Staging';
+
+-- Create with properties
+CREATE CONFIGURATION 'Production'
+  DatabaseType = 'POSTGRESQL',
+  DatabaseUrl = 'prod-db:5432',
+  HttpPortNumber = 8080;
+
+-- Drop a configuration
+DROP CONFIGURATION 'Staging';
 ```
 
 ### Language and Workflow Settings

cmd/mxcli/help_topics/constant.txt

@@ -24,6 +24,9 @@ Show constant values across configurations:
   SHOW CONSTANT VALUES;              -- All constants with per-config overrides
   SHOW CONSTANT VALUES IN MyModule;  -- Filter by module
 
+Remove a constant override from a configuration:
+  ALTER SETTINGS DROP CONSTANT 'Module.Name' IN CONFIGURATION 'cfg';
+
 Describe a constant:
   DESCRIBE CONSTANT Module.Name;
 

cmd/mxcli/help_topics/settings.txt

@@ -34,6 +34,21 @@ ALTER SETTINGS (Constant Overrides)
   ALTER SETTINGS CONSTANT 'BusinessEvents.ServerUrl' VALUE 'kafka:9092'
     IN CONFIGURATION 'Default';
 
+  ALTER SETTINGS DROP CONSTANT 'BusinessEvents.ServerUrl'
+    IN CONFIGURATION 'Default';              -- Remove override (reset to default)
+
+CREATE / DROP CONFIGURATION
+----------------------------
+
+  CREATE CONFIGURATION 'Staging';            -- Create with defaults
+
+  CREATE CONFIGURATION 'Production'
+    DatabaseType = 'POSTGRESQL',
+    DatabaseUrl = 'prod-db:5432',
+    HttpPortNumber = 8080;                   -- Create with properties
+
+  DROP CONFIGURATION 'Staging';              -- Remove a configuration
+
 ALTER SETTINGS (Language / Workflows)
 -------------------------------------
 

docs-site/src/reference/settings/alter-settings.md

@@ -8,6 +8,12 @@
 
     ALTER SETTINGS CONSTANT 'name' VALUE 'value' IN CONFIGURATION 'config'
 
+    ALTER SETTINGS DROP CONSTANT 'name' IN CONFIGURATION 'config'
+
+    CREATE CONFIGURATION 'name' [key = value, ...]
+
+    DROP CONFIGURATION 'name'
+
     ALTER SETTINGS LANGUAGE key = value
 
     ALTER SETTINGS WORKFLOWS key = value
@@ -84,6 +90,27 @@ ALTER SETTINGS WORKFLOWS UserEntity = 'Administration.Account';
 ALTER SETTINGS MODEL JavaVersion = '17';
 ```
 
+### Remove a constant override from a configuration
+
+```sql
+ALTER SETTINGS DROP CONSTANT 'MyModule.ApiBaseUrl' IN CONFIGURATION 'staging';
+```
+
+### Create a new configuration
+
+```sql
+CREATE CONFIGURATION 'Staging'
+  DatabaseType = 'POSTGRESQL',
+  DatabaseUrl = 'staging-db:5432',
+  HttpPortNumber = 8080;
+```
+
+### Drop a configuration
+
+```sql
+DROP CONFIGURATION 'Staging';
+```
+
 ## See Also
 
 [SHOW / DESCRIBE SETTINGS](show-settings.md)

docs/01-project/MDL_QUICK_REFERENCE.md

@@ -293,6 +293,9 @@ CREATE OR REPLACE NAVIGATION Responsive
 | Alter model settings | `ALTER SETTINGS MODEL Key = Value;` | AfterStartupMicroflow, HashAlgorithm, JavaVersion, etc. |
 | Alter configuration | `ALTER SETTINGS CONFIGURATION 'Name' Key = Value;` | DatabaseType, DatabaseUrl, HttpPortNumber, etc. |
 | Alter constant | `ALTER SETTINGS CONSTANT 'Name' VALUE 'val' IN CONFIGURATION 'cfg';` | Override constant per configuration |
+| Drop constant override | `ALTER SETTINGS DROP CONSTANT 'Name' IN CONFIGURATION 'cfg';` | Reset to default value |
+| Create configuration | `CREATE CONFIGURATION 'Name' [Key = Value, ...];` | New server configuration |
+| Drop configuration | `DROP CONFIGURATION 'Name';` | Remove a configuration |
 | Alter language | `ALTER SETTINGS LANGUAGE Key = Value;` | DefaultLanguageCode |
 | Alter workflows | `ALTER SETTINGS WORKFLOWS Key = Value;` | UserEntity, DefaultTaskParallelism |
 

docs/05-mdl-specification/01-language-reference.md

@@ -1177,10 +1177,18 @@ Displays one row per constant per configuration. Shows the default value followe
 ALTER SETTINGS MODEL Key = Value;
 ALTER SETTINGS CONFIGURATION 'Name' Key = Value;
 ALTER SETTINGS CONSTANT 'Name' VALUE 'val' IN CONFIGURATION 'cfg';
+ALTER SETTINGS DROP CONSTANT 'Name' IN CONFIGURATION 'cfg';
 ALTER SETTINGS LANGUAGE Key = Value;
 ALTER SETTINGS WORKFLOWS Key = Value;
 ```
 
+### CREATE / DROP CONFIGURATION
+
+```sql
+CREATE CONFIGURATION 'Name' [Key = Value, ...];
+DROP CONFIGURATION 'Name';
+```
+
 **Example:**
 ```sql
 ALTER SETTINGS MODEL AfterStartupMicroflow = 'MyModule.ACT_Startup';
@@ -1189,6 +1197,15 @@ ALTER SETTINGS LANGUAGE DefaultLanguageCode = 'en_US';
 
 -- View constant values across all configurations
 SHOW CONSTANT VALUES;
+
+-- Create a new configuration
+CREATE CONFIGURATION 'Staging' DatabaseType = 'POSTGRESQL', DatabaseUrl = 'staging-db:5432';
+
+-- Remove a constant override
+ALTER SETTINGS DROP CONSTANT 'MyModule.ApiKey' IN CONFIGURATION 'Default';
+
+-- Drop a configuration
+DROP CONFIGURATION 'Staging';
 ```
 
 ---

mdl/ast/ast_settings.go

@@ -8,8 +8,24 @@ type AlterSettingsStmt struct {
 	ConfigName string         // For CONFIGURATION section: the configuration name (e.g., "Default")
 	Properties map[string]any // Key-value pairs to set
 	// For CONSTANT section:
-	ConstantId string // Qualified constant name
-	Value      string // Constant value
+	ConstantId    string // Qualified constant name
+	Value         string // Constant value
+	DropConstant  bool   // If true, remove the constant override instead of setting it
 }
 
 func (s *AlterSettingsStmt) isStatement() {}
+
+// CreateConfigurationStmt represents CREATE CONFIGURATION 'name' [properties...].
+type CreateConfigurationStmt struct {
+	Name       string
+	Properties map[string]any
+}
+
+func (s *CreateConfigurationStmt) isStatement() {}
+
+// DropConfigurationStmt represents DROP CONFIGURATION 'name'.
+type DropConfigurationStmt struct {
+	Name string
+}
+
+func (s *DropConfigurationStmt) isStatement() {}

mdl/executor/cmd_settings.go

@@ -348,6 +348,22 @@ func (e *Executor) alterSettingsConstant(ps *model.ProjectSettings, stmt *ast.Al
 		return fmt.Errorf("configuration not found: %s", targetConfig)
 	}
 
+	if stmt.DropConstant {
+		// Remove the constant override
+		for i, cv := range cfg.ConstantValues {
+			if cv.ConstantId == stmt.ConstantId {
+				cfg.ConstantValues = append(cfg.ConstantValues[:i], cfg.ConstantValues[i+1:]...)
+				if err := e.writer.UpdateProjectSettings(ps); err != nil {
+					return fmt.Errorf("failed to update project settings: %w", err)
+				}
+				fmt.Fprintf(e.output, "Dropped constant '%s' from configuration '%s'\n",
+					stmt.ConstantId, targetConfig)
+				return nil
+			}
+		}
+		return fmt.Errorf("constant '%s' not found in configuration '%s'", stmt.ConstantId, targetConfig)
+	}
+
 	// Find or create the constant value
 	found := false
 	for _, cv := range cfg.ConstantValues {
@@ -375,6 +391,107 @@ func (e *Executor) alterSettingsConstant(ps *model.ProjectSettings, stmt *ast.Al
 	return nil
 }
 
+// createConfiguration handles CREATE CONFIGURATION 'name' [properties...].
+func (e *Executor) createConfiguration(stmt *ast.CreateConfigurationStmt) error {
+	if e.writer == nil {
+		return fmt.Errorf("not connected in write mode")
+	}
+
+	ps, err := e.reader.GetProjectSettings()
+	if err != nil {
+		return fmt.Errorf("failed to read project settings: %w", err)
+	}
+
+	if ps.Configuration == nil {
+		return fmt.Errorf("configuration settings not found in project")
+	}
+
+	// Check if configuration already exists
+	for _, cfg := range ps.Configuration.Configurations {
+		if strings.EqualFold(cfg.Name, stmt.Name) {
+			return fmt.Errorf("configuration already exists: %s", stmt.Name)
+		}
+	}
+
+	newCfg := &model.ServerConfiguration{
+		Name:           stmt.Name,
+		DatabaseType:   "HSQLDB",
+		HttpPortNumber: 8080,
+		ConstantValues: []*model.ConstantValue{},
+	}
+	newCfg.TypeName = "Settings$ServerConfiguration"
+
+	// Apply optional properties
+	for key, val := range stmt.Properties {
+		valStr := settingsValueToString(val)
+		switch key {
+		case "DatabaseType":
+			newCfg.DatabaseType = valStr
+		case "DatabaseUrl":
+			newCfg.DatabaseUrl = valStr
+		case "DatabaseName":
+			newCfg.DatabaseName = valStr
+		case "DatabaseUserName":
+			newCfg.DatabaseUserName = valStr
+		case "DatabasePassword":
+			newCfg.DatabasePassword = valStr
+		case "HttpPortNumber":
+			if v, err := strconv.Atoi(valStr); err == nil {
+				newCfg.HttpPortNumber = v
+			}
+		case "ServerPortNumber":
+			if v, err := strconv.Atoi(valStr); err == nil {
+				newCfg.ServerPortNumber = v
+			}
+		case "ApplicationRootUrl":
+			newCfg.ApplicationRootUrl = valStr
+		default:
+			return fmt.Errorf("unknown configuration property: %s", key)
+		}
+	}
+
+	ps.Configuration.Configurations = append(ps.Configuration.Configurations, newCfg)
+
+	if err := e.writer.UpdateProjectSettings(ps); err != nil {
+		return fmt.Errorf("failed to update project settings: %w", err)
+	}
+
+	fmt.Fprintf(e.output, "Created configuration: %s\n", stmt.Name)
+	return nil
+}
+
+// dropConfiguration handles DROP CONFIGURATION 'name'.
+func (e *Executor) dropConfiguration(stmt *ast.DropConfigurationStmt) error {
+	if e.writer == nil {
+		return fmt.Errorf("not connected in write mode")
+	}
+
+	ps, err := e.reader.GetProjectSettings()
+	if err != nil {
+		return fmt.Errorf("failed to read project settings: %w", err)
+	}
+
+	if ps.Configuration == nil {
+		return fmt.Errorf("configuration settings not found in project")
+	}
+
+	for i, cfg := range ps.Configuration.Configurations {
+		if strings.EqualFold(cfg.Name, stmt.Name) {
+			ps.Configuration.Configurations = append(
+				ps.Configuration.Configurations[:i],
+				ps.Configuration.Configurations[i+1:]...,
+			)
+			if err := e.writer.UpdateProjectSettings(ps); err != nil {
+				return fmt.Errorf("failed to update project settings: %w", err)
+			}
+			fmt.Fprintf(e.output, "Dropped configuration: %s\n", stmt.Name)
+			return nil
+		}
+	}
+
+	return fmt.Errorf("configuration not found: %s", stmt.Name)
+}
+
 // settingsValueToString converts an AST settings value to string.
 func settingsValueToString(val any) string {
 	switch v := val.(type) {

mdl/executor/executor.go

@@ -295,6 +295,10 @@ func (e *Executor) executeInner(stmt ast.Statement) error {
 	// Settings statements
 	case *ast.AlterSettingsStmt:
 		return e.alterSettings(s)
+	case *ast.CreateConfigurationStmt:
+		return e.createConfiguration(s)
+	case *ast.DropConfigurationStmt:
+		return e.dropConfiguration(s)
 
 	// OData statements
 	case *ast.CreateODataClientStmt:

mdl/grammar/MDLParser.g4

@@ -98,6 +98,7 @@ createStatement
       | createUserRoleStatement
       | createDemoUserStatement
       | createImageCollectionStatement
+      | createConfigurationStatement
       )
     ;
 
@@ -251,6 +252,7 @@ dropStatement
     | DROP WORKFLOW qualifiedName
     | DROP IMAGE COLLECTION qualifiedName
     | DROP REST CLIENT qualifiedName
+    | DROP CONFIGURATION STRING_LITERAL
     | DROP FOLDER STRING_LITERAL IN (qualifiedName | IDENTIFIER)
     ;
 
@@ -2014,6 +2016,11 @@ constantOption
     | EXPOSED TO CLIENT
     ;
 
+createConfigurationStatement
+    : CONFIGURATION STRING_LITERAL
+      (settingsAssignment (COMMA settingsAssignment)*)?
+    ;
+
 /**
  * CREATE REST CLIENT Module.Name
  * BASE URL 'https://api.example.com/v1'
@@ -2397,7 +2404,8 @@ workflowAnnotationStmt
  */
 alterSettingsClause
     : settingsSection settingsAssignment (COMMA settingsAssignment)*
-    | CONSTANT STRING_LITERAL VALUE settingsValue (IN CONFIGURATION STRING_LITERAL)?
+    | CONSTANT STRING_LITERAL (VALUE settingsValue | DROP) (IN CONFIGURATION STRING_LITERAL)?
+    | DROP CONSTANT STRING_LITERAL (IN CONFIGURATION STRING_LITERAL)?
     | CONFIGURATION STRING_LITERAL settingsAssignment (COMMA settingsAssignment)*
     ;