Fix nil crashes

rules.go

@@ -203,43 +203,54 @@ func FieldsOnCorrectTypeRule(context *ValidationContext) *ValidationRuleInstance
 					if node, ok := p.Node.(*ast.Field); ok {
 						ttype := context.ParentType()
 
-						if ttype != nil {
-							fieldDef := context.FieldDef()
-							if fieldDef == nil {
-								// This isn't valid. Let's find suggestions, if any.
-								suggestedTypes := []string{}
+						if ttype == nil {
+							return action, result
+						}
+						if t, ok := ttype.(*Object); ok && t == nil {
+							return action, result
+						}
+						if t, ok := ttype.(*Interface); ok && t == nil {
+							return action, result
+						}
+						if t, ok := ttype.(*Union); ok && t == nil {
+							return action, result
+						}
 
-								nodeName := ""
-								if node.Name != nil {
-									nodeName = node.Name.Value
-								}
+						fieldDef := context.FieldDef()
+						if fieldDef == nil {
+							// This isn't valid. Let's find suggestions, if any.
+							suggestedTypes := []string{}
+
+							nodeName := ""
+							if node.Name != nil {
+								nodeName = node.Name.Value
+							}
 
-								if ttype, ok := ttype.(Abstract); ok && IsAbstractType(ttype) {
-									siblingInterfaces := getSiblingInterfacesIncludingField(context.Schema(), ttype, nodeName)
-									implementations := getImplementationsIncludingField(context.Schema(), ttype, nodeName)
-									suggestedMaps := map[string]bool{}
-									for _, s := range siblingInterfaces {
-										if _, ok := suggestedMaps[s]; !ok {
-											suggestedMaps[s] = true
-											suggestedTypes = append(suggestedTypes, s)
-										}
+							if ttype, ok := ttype.(Abstract); ok && IsAbstractType(ttype) {
+								siblingInterfaces := getSiblingInterfacesIncludingField(context.Schema(), ttype, nodeName)
+								implementations := getImplementationsIncludingField(context.Schema(), ttype, nodeName)
+								suggestedMaps := map[string]bool{}
+								for _, s := range siblingInterfaces {
+									if _, ok := suggestedMaps[s]; !ok {
+										suggestedMaps[s] = true
+										suggestedTypes = append(suggestedTypes, s)
 									}
-									for _, s := range implementations {
-										if _, ok := suggestedMaps[s]; !ok {
-											suggestedMaps[s] = true
-											suggestedTypes = append(suggestedTypes, s)
-										}
+								}
+								for _, s := range implementations {
+									if _, ok := suggestedMaps[s]; !ok {
+										suggestedMaps[s] = true
+										suggestedTypes = append(suggestedTypes, s)
 									}
 								}
+							}
 
-								message := UndefinedFieldMessage(nodeName, ttype.Name(), suggestedTypes)
+							message := UndefinedFieldMessage(nodeName, ttype.Name(), suggestedTypes)
 
-								reportError(
-									context,
-									message,
-									[]ast.Node{node},
-								)
-							}
+							reportError(
+								context,
+								message,
+								[]ast.Node{node},
+							)
 						}
 					}
 					return action, result
@@ -1073,10 +1084,10 @@ func collectFieldASTsAndDefs(context *ValidationContext, parentType Named, selec
 				fieldName = selection.Name.Value
 			}
 			var fieldDef *FieldDefinition
-			if parentType, ok := parentType.(*Object); ok {
+			if parentType, ok := parentType.(*Object); ok && parentType != nil {
 				fieldDef, _ = parentType.Fields()[fieldName]
 			}
-			if parentType, ok := parentType.(*Interface); ok {
+			if parentType, ok := parentType.(*Interface); ok && parentType != nil {
 				fieldDef, _ = parentType.Fields()[fieldName]
 			}
 
@@ -2119,6 +2130,9 @@ func VariablesInAllowedPositionRule(context *ValidationContext) *ValidationRuleI
 func isValidLiteralValue(ttype Input, valueAST ast.Value) (bool, []string) {
 	// A value must be provided if the type is non-null.
 	if ttype, ok := ttype.(*NonNull); ok {
+		if e := ttype.Error(); e != nil {
+			return false, []string{e.Error()}
+		}
 		if valueAST == nil {
 			if ttype.OfType.Name() != "" {
 				return false, []string{fmt.Sprintf(`Expected "%v!", found null.`, ttype.OfType.Name())}

rules_default_values_of_correct_type_test.go

@@ -101,3 +101,7 @@ func TestValidate_VariableDefaultValuesOfCorrectType_ListVariablesWithInvalidIte
 				2, 40),
 		})
 }
+
+func TestValidate_VariableDefaultValuesOfCorrectType_InvalidNonNull(t *testing.T) {
+	testutil.ExpectPassesRule(t, graphql.DefaultValuesOfCorrectTypeRule, `query($g:e!){a}`)
+}

rules_fields_on_correct_type_test.go

@@ -209,3 +209,7 @@ func TestValidate_FieldsOnCorrectTypeErrorMessage_WorksWithLotsOfSuggestions(t *
 		t.Fatalf("Unexpected message, expected: %v, got %v", expected, message)
 	}
 }
+
+func TestValidate_FieldsOnCorrectType_NilCrash(t *testing.T) {
+	testutil.ExpectPassesRule(t, graphql.FieldsOnCorrectTypeRule, `mutation{o}`)
+}

rules_overlapping_fields_can_be_merged_test.go

@@ -729,3 +729,7 @@ func TestValidate_OverlappingFieldsCanBeMerged_ReturnTypesMustBeUnambiguous_Igno
         }
     `)
 }
+
+func TestValidate_OverlappingFieldsCanBeMerged_NilCrash(t *testing.T) {
+	testutil.ExpectPassesRule(t, graphql.OverlappingFieldsCanBeMergedRule, `subscription {e}`)
+}

type_info.go

@@ -252,14 +252,14 @@ func DefaultTypeInfoFieldDef(schema *Schema, parentType Type, fieldAST *ast.Fiel
 		schema.QueryType() == parentType {
 		return TypeMetaFieldDef
 	}
-	if name == TypeNameMetaFieldDef.Name {
-		if _, ok := parentType.(*Object); ok && parentType != nil {
+	if name == TypeNameMetaFieldDef.Name && parentType != nil {
+		if t, ok := parentType.(*Object); ok && t != nil {
 			return TypeNameMetaFieldDef
 		}
-		if _, ok := parentType.(*Interface); ok && parentType != nil {
+		if t, ok := parentType.(*Interface); ok && t != nil {
 			return TypeNameMetaFieldDef
 		}
-		if _, ok := parentType.(*Union); ok && parentType != nil {
+		if t, ok := parentType.(*Union); ok && t != nil {
 			return TypeNameMetaFieldDef
 		}
 	}