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: 2 people

mdl/ast/ast_query.go

@@ -436,8 +436,10 @@ 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"
 	mdlerrors "github.com/mendixlabs/mxcli/mdl/errors"
 	"github.com/mendixlabs/mxcli/mdl/visitor"
@@ -50,8 +51,22 @@ func execSet(ctx *ExecContext, s *ast.SetStmt) error {
 	return nil
 }
 
-// execHelp handles HELP statements.
-func execHelp(ctx *ExecContext) error {
+// execHelp handles HELP statements. With topic words, queries the syntax registry.
+func execHelp(ctx *ExecContext, s *ast.HelpStmt) error {
+	if len(s.Topic) > 0 {
+		path := resolveHelpPath(s.Topic)
+		features := syntax.ByPrefix(path)
+		if len(features) == 0 {
+			fmt.Fprintf(ctx.Output, "No syntax help found for: %s\n", path)
+			fmt.Fprintln(ctx.Output, "Use HELP; for a command overview.")
+			return nil
+		}
+		if ctx.Format == FormatJSON {
+			return syntax.WriteJSON(ctx.Output, features)
+		}
+		syntax.WriteText(ctx.Output, features)
+		return nil
+	}
 	help := `MDL Commands:
 
 Connection:
@@ -328,6 +343,32 @@ 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, ".")
+}
+
 // listVersion displays Mendix project version information.
 func listVersion(ctx *ExecContext) error {
 	if !ctx.Connected() {

mdl/executor/executor_dispatch.go

@@ -33,3 +33,6 @@ func (e *Executor) newExecContext(ctx context.Context) *ExecContext {
 		executor:      e,
 	}
 }
+
+// Ensure ast import is used via executeInner's stmt parameter.
+var _ ast.Statement = (*ast.HelpStmt)(nil)

mdl/executor/register_stubs.go

@@ -376,7 +376,7 @@ func registerSessionHandlers(r *Registry) {
 		return execSet(ctx, stmt.(*ast.SetStmt))
 	})
 	r.Register(&ast.HelpStmt{}, func(ctx *ExecContext, stmt ast.Statement) error {
-		return execHelp(ctx)
+		return execHelp(ctx, stmt.(*ast.HelpStmt))
 	})
 	r.Register(&ast.ExitStmt{}, func(ctx *ExecContext, stmt ast.Statement) error {
 		return execExit(ctx)

mdl/grammar/MDLParser.g4

@@ -3483,7 +3483,7 @@ linkMapping
     ;
 
 helpStatement
-    : IDENTIFIER  // HELP command
+    : IDENTIFIER (identifierOrKeyword)*  // HELP [topic words...]
     ;
 
 /**

mdl/grammar/parser/MDLParser.interp

@@ -1004,13 +1004,17 @@ 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":