fix: no need to mark param optional if default value is given (#2879)

Author: saihaj

src/language/blockString.js

@@ -93,8 +93,8 @@ export function getBlockStringIndentation(value: string): number {
  */
 export function printBlockString(
   value: string,
-  indentation?: string = '',
-  preferMultipleLines?: boolean = false,
+  indentation: string = '',
+  preferMultipleLines: boolean = false,
 ): string {
   const isSingleLine = value.indexOf('\n') === -1;
   const hasLeadingSpace = value[0] === ' ' || value[0] === '\t';

src/utilities/coerceInputValue.js

@@ -33,7 +33,7 @@ type OnErrorCB = (
 export function coerceInputValue(
   inputValue: mixed,
   type: GraphQLInputType,
-  onError?: OnErrorCB = defaultOnError,
+  onError: OnErrorCB = defaultOnError,
 ): mixed {
   return coerceInputValueImpl(inputValue, type, onError);
 }

src/validation/validate.js

@@ -33,9 +33,9 @@ import { SDLValidationContext, ValidationContext } from './ValidationContext';
 export function validate(
   schema: GraphQLSchema,
   documentAST: DocumentNode,
-  rules?: $ReadOnlyArray<ValidationRule> = specifiedRules,
-  typeInfo?: TypeInfo = new TypeInfo(schema),
-  options?: {| maxErrors?: number |} = { maxErrors: undefined },
+  rules: $ReadOnlyArray<ValidationRule> = specifiedRules,
+  typeInfo: TypeInfo = new TypeInfo(schema),
+  options: {| maxErrors?: number |} = { maxErrors: undefined },
 ): $ReadOnlyArray<GraphQLError> {
   devAssert(documentAST, 'Must provide document.');
   // If the schema used for validation is invalid, throw an error.
@@ -81,7 +81,7 @@ export function validate(
 export function validateSDL(
   documentAST: DocumentNode,
   schemaToExtend?: ?GraphQLSchema,
-  rules?: $ReadOnlyArray<SDLValidationRule> = specifiedSDLRules,
+  rules: $ReadOnlyArray<SDLValidationRule> = specifiedSDLRules,
 ): $ReadOnlyArray<GraphQLError> {
   const errors = [];
   const context = new SDLValidationContext(