fix: Fix bug signature help

Author: lighttiger2505

internal/handler/signature_help_test.go

@@ -20,7 +20,7 @@ type signatureHelpTestCase struct {
 
 var signatureHelpTestCases = []signatureHelpTestCase{
 	// single record
-	// input is "insert into city (ID, Name, CountryCode) VALUES (123, 'aaa', '2020')"
+	// input is "insert into city (ID, Name, CountryCode) VALUES (123,  NULL, '2020')"
 	genSingleRecordInsertTest(50, 0),
 	genSingleRecordInsertTest(52, 0),
 	genSingleRecordInsertTest(53, 1),
@@ -48,7 +48,7 @@ var signatureHelpTestCases = []signatureHelpTestCase{
 func genSingleRecordInsertTest(col int, wantActiveParameter int) signatureHelpTestCase {
 	return signatureHelpTestCase{
 		name:  fmt.Sprintf("single record %d-%d", col, wantActiveParameter),
-		input: "insert into city (ID, Name, CountryCode) VALUES (123, 'aaa', '2020')",
+		input: "insert into city (ID, Name, CountryCode) VALUES (123,  NULL, '2020')",
 		line:  0,
 		col:   col,
 		want: lsp.SignatureHelp{

parser/parser.go

@@ -550,6 +550,9 @@ var identifierListTargetMatcher = astutil.NodeMatcher{
 		ast.TypeOperator,
 		ast.TypeSwitchCase,
 	},
+	ExpectKeyword: []string{
+		"NULL",
+	},
 }
 
 func parseIdentifierList(reader *astutil.NodeReader) ast.Node {

parser/parser_test.go

@@ -983,6 +983,15 @@ func TestParseIdentifierList(t *testing.T) {
 				testIdentifierList(t, list[0], input)
 			},
 		},
+		{
+			name:  "with null",
+			input: "foo, null, foobar",
+			checkFn: func(t *testing.T, stmts []*ast.Statement, input string) {
+				testStatement(t, stmts[0], 1, input)
+				list := stmts[0].GetTokens()
+				testIdentifierList(t, list[0], input)
+			},
+		},
 		{
 			name:  "invalid single identifer without whitespace",
 			input: "foo,",