feat: HELP command with topic parameters (Phase 3)

HELP WORKFLOW; HELP WORKFLOW USER TASK; HELP SECURITY ENTITY ACCESS;
all now query the syntax feature registry. Greedy path resolver
merges space-separated words into hyphenated registry paths.

Grammar extended: helpStatement accepts optional identifierOrKeyword*.
AST HelpStmt gains Topic []string field.

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

Author: engalar

mdl/ast/ast_query.go

@@ -406,8 +406,10 @@ type SetStmt struct {
 
 func (s *SetStmt) isStatement() {}
 
-// HelpStmt represents: HELP or ?
-type HelpStmt struct{}
+// HelpStmt represents: HELP [topic words...]
+type HelpStmt struct {
+	Topic []string // e.g., ["workflow", "user-task"] for HELP WORKFLOW USER-TASK
+}
 
 func (s *HelpStmt) isStatement() {}
 

mdl/executor/cmd_misc.go

@@ -10,6 +10,7 @@ import (
 	"path/filepath"
 	"strings"
 
+	"github.com/mendixlabs/mxcli/cmd/mxcli/syntax"
 	"github.com/mendixlabs/mxcli/mdl/ast"
 	"github.com/mendixlabs/mxcli/mdl/visitor"
 )
@@ -42,8 +43,22 @@ func (e *Executor) execSet(s *ast.SetStmt) error {
 	return nil
 }
 
-// execHelp handles HELP statements.
-func (e *Executor) execHelp() error {
+// execHelp handles HELP statements. With topic words, queries the syntax registry.
+func (e *Executor) execHelp(s *ast.HelpStmt) error {
+	if len(s.Topic) > 0 {
+		path := resolveHelpPath(s.Topic)
+		features := syntax.ByPrefix(path)
+		if len(features) == 0 {
+			fmt.Fprintf(e.output, "No syntax help found for: %s\n", path)
+			fmt.Fprintln(e.output, "Use HELP; for a command overview.")
+			return nil
+		}
+		if e.format == FormatJSON {
+			return syntax.WriteJSON(e.output, features)
+		}
+		syntax.WriteText(e.output, features)
+		return nil
+	}
 	help := `MDL Commands:
 
 Connection:
@@ -320,6 +335,32 @@ Statement Terminator:
 	return nil
 }
 
+// resolveHelpPath converts space-separated words like ["workflow", "user", "task"]
+// into a registry path like "workflow.user-task" by greedily merging adjacent words
+// with hyphens to find the longest matching prefix at each level.
+func resolveHelpPath(words []string) string {
+	var segments []string
+	i := 0
+	for i < len(words) {
+		matched := false
+		for j := len(words); j > i; j-- {
+			candidate := strings.Join(words[i:j], "-")
+			testPath := strings.Join(append(segments, candidate), ".")
+			if syntax.HasPrefix(testPath) {
+				segments = append(segments, candidate)
+				i = j
+				matched = true
+				break
+			}
+		}
+		if !matched {
+			segments = append(segments, words[i])
+			i++
+		}
+	}
+	return strings.Join(segments, ".")
+}
+
 // showVersion displays Mendix project version information.
 func (e *Executor) showVersion() error {
 	if e.reader == nil {

mdl/executor/executor_dispatch.go

@@ -251,7 +251,7 @@ func (e *Executor) executeInner(stmt ast.Statement) error {
 	case *ast.SetStmt:
 		return e.execSet(s)
 	case *ast.HelpStmt:
-		return e.execHelp()
+		return e.execHelp(s)
 	case *ast.ExitStmt:
 		return e.execExit()
 	case *ast.ExecuteScriptStmt:

mdl/grammar/MDLParser.g4

@@ -3350,7 +3350,7 @@ linkMapping
     ;
 
 helpStatement
-    : IDENTIFIER  // HELP command
+    : IDENTIFIER (identifierOrKeyword)*  // HELP [topic words...]
     ;
 
 /**

mdl/grammar/parser/MDLParser.interp

@@ -916,13 +916,17 @@ func (b *Builder) ExitExecuteScriptStatement(ctx *parser.ExecuteScriptStatementC
 }
 
 // ExitHelpStatement handles help/exit/quit commands
-// Grammar: helpStatement: IDENTIFIER
+// Grammar: helpStatement: IDENTIFIER (identifierOrKeyword)*
 func (b *Builder) ExitHelpStatement(ctx *parser.HelpStatementContext) {
 	if id := ctx.IDENTIFIER(); id != nil {
 		cmd := strings.ToLower(id.GetText())
 		switch cmd {
 		case "help", "?":
-			b.statements = append(b.statements, &ast.HelpStmt{})
+			stmt := &ast.HelpStmt{}
+			for _, tok := range ctx.AllIdentifierOrKeyword() {
+				stmt.Topic = append(stmt.Topic, strings.ToLower(tok.GetText()))
+			}
+			b.statements = append(b.statements, stmt)
 		case "exit", "quit":
 			b.statements = append(b.statements, &ast.ExitStmt{})
 		case "status":