Analysis support for table-valued functions

sqlparser/lib/src/analysis/steps/column_resolver.dart

@@ -136,16 +136,9 @@ class ColumnResolver extends RecursiveVisitor<void, void> {
         }
       },
       isTableFunction: (function) {
-        final functions = context.engineOptions.addedFunctions;
-        final lowercaseName = function.name.toLowerCase();
-        ResultSet resolved;
-
-        if (functions.containsKey(lowercaseName)) {
-          final handler = functions[lowercaseName];
-          if (handler is TableValuedFunctionHandler) {
-            resolved = handler.resolveTableValued(context, function);
-          }
-        }
+        final handler = context
+            .engineOptions.addedTableFunctions[function.name.toLowerCase()];
+        final resolved = handler?.resolveTableValued(context, function);
 
         if (resolved == null) {
           context.reportError(AnalysisError(

sqlparser/lib/src/ast/expressions/function.dart

@@ -1,7 +1,11 @@
 part of '../ast.dart';
 
-/// Interface for function calls, either a [FunctionExpression] or a
-/// [AggregateExpression].
+/// Interface for function calls.
+///
+/// Functions that resolve to an [Expression] are subclasses of
+/// [ExpressionInvocation], like [FunctionExpression] or [AggregateExpression].
+/// There are invocation that don't resolve to an expression, notably
+/// [TableValuedFunction].
 abstract class SqlInvocation implements AstNode {
   /// The name of the function being called
   String get name;

sqlparser/lib/src/engine/module/module.dart

@@ -47,7 +47,12 @@ abstract class FunctionHandler {
   void reportErrors(SqlInvocation call, AnalysisContext context) {}
 }
 
-abstract class TableValuedFunctionHandler implements FunctionHandler {
+/// Interface for a handler which can resolve the result set of a table-valued
+/// function.
+abstract class TableValuedFunctionHandler {
+  /// The name of the table-valued function implemented by this handler.
+  String get functionName;
+
   /// Resolve the result set of a table-valued function.
   ///
   /// Should return null when the result set can't be resolved.

sqlparser/lib/src/engine/options.dart

@@ -16,8 +16,14 @@ class EngineOptions {
   final List<Extension> enabledExtensions;
 
   final List<FunctionHandler> _addedFunctionHandlers = [];
+
+  /// A map from lowercase function names to the associated handler.
   final Map<String, FunctionHandler> addedFunctions = {};
 
+  /// A map from lowercase function names (where the function is a table-valued
+  /// function) to the associated handler.
+  final Map<String, TableValuedFunctionHandler> addedTableFunctions = {};
+
   EngineOptions({
     this.useMoorExtensions = false,
     this.enableJson1 = false,
@@ -32,4 +38,8 @@ class EngineOptions {
       addedFunctions[function.toLowerCase()] = handler;
     }
   }
+
+  void addTableValuedFunctionHandler(TableValuedFunctionHandler handler) {
+    addedTableFunctions[handler.functionName.toLowerCase()] = handler;
+  }
 }

sqlparser/lib/src/engine/sql_engine.dart

@@ -75,6 +75,12 @@ class SqlEngine {
     options.addFunctionHandler(handler);
   }
 
+  /// Registers the [handler], which can infer result sets for a table-valued
+  /// function.
+  void registerTableValuedFunctionHandler(TableValuedFunctionHandler handler) {
+    options.addTableValuedFunctionHandler(handler);
+  }
+
   ReferenceScope _constructRootScope({ReferenceScope parent}) {
     final scope = parent == null ? ReferenceScope(null) : parent.createChild();
     for (final table in knownTables) {