feat(dts-generator): support optional parameters in function types

Author: codeworrior

packages/dts-generator/src/phases/dts-code-gen.ts

@@ -867,7 +867,7 @@ function genType(ast: Type, usage: string = "unknown"): string {
       if (!_.isEmpty(ast.typeParameters)) {
         text += `<${_.map(ast.typeParameters, (param) => param.name).join(", ")}>`; // TODO defaults, constraints, expressions
       }
-      text += `(${_.map(ast.parameters, (param) => `${param.name}: ${genType(param.type, "parameter")}`).join(", ")})`;
+      text += `(${_.map(ast.parameters, (param) => `${param.name}${param.optional ? "?" : ""}: ${genType(param.type, "parameter")}`).join(", ")})`;
       text += ` => ${ast.type ? genType(ast.type, "returnValue") : "void"}`;
       return text;
     case "NativeTSTypeExpression":

packages/dts-generator/src/utils/ts-ast-type-builder.ts

@@ -114,6 +114,7 @@ export class TSASTTypeBuilder {
       kind: "Parameter",
       name: "p" + (idx + 1), // JSDoc function types don't allow parameter names -> generate names
       type: param,
+      optional: (param as any).optional,
     }));
     if (thisType != null) {
       // for TS, a 'this' type is specified as the first parameter type of a function