Last signature is missing when multiple are defined

[ST-DDT]

Search terms

• signature
• missing

Expected Behavior

If I scan a method with multiple signatures, then I expect all of them to be present in the typedoc.json/reflection data.

Actual Behavior

The last one is always missing.
I need that at least for the default value.

Steps to reproduce the bug

export class SignatureTest {
  /**
   * Test with multiple signatures.
   *
   * @param a The value to return.
   */
  multiSignature(a: boolean): boolean;
  multiSignature(a: number): number;
  multiSignature(a: unknown = 1): unknown {
    return a;
  }
}

typedoc.json

{
	"id": 0,
	"name": "@faker-js/faker",
	"kind": 1,
	"kindString": "Project",
	"flags": {},
	"originalName": "",
	"children": [
		{
			"id": 1,
			"name": "SignatureTest",
			"kind": 128,
			"kindString": "Class",
			"flags": {},
			"children": [
[...]
				{
					"id": 4,
					"name": "multiSignature",
					"kind": 2048,
					"kindString": "Method",
					"flags": {},
					"sources": [...]
					"signatures": [
						{
							"id": 5,
							"name": "multiSignature",
							"kind": 4096,
							"kindString": "Call signature",
							"flags": {},
							"comment": {
								"shortText": "Test with multiple signatures."
							},
							"parameters": [
								{
									"id": 6,
									"name": "a",
									"kind": 32768,
									"kindString": "Parameter",
									"flags": {},
									"comment": {
										"shortText": "The value to return.\n"
									},
									"type": {
										"type": "intrinsic",
										"name": "boolean"
									}
								}
							],
							"type": {
								"type": "intrinsic",
								"name": "boolean"
							}
						},
						{
							"id": 7,
							"name": "multiSignature",
							"kind": 4096,
							"kindString": "Call signature",
							"flags": {},
							"parameters": [
								{
									"id": 8,
									"name": "a",
									"kind": 32768,
									"kindString": "Parameter",
									"flags": {},
									"type": {
										"type": "intrinsic",
										"name": "number"
									}
								}
							],
							"type": {
								"type": "intrinsic",
								"name": "number"
							}
						},
+						{
+							"id": 9,
+							"name": "multiSignature",
+							"kind": 4096,
+							"kindString": "Call signature",
+							"flags": {},
+							"parameters": [
+								{
+									"id": 10,
+									"name": "a",
+									"kind": 32768,
+									"kindString": "Parameter",
+									"flags": {},
+									"type": {
+										"type": "intrinsic",
+										"name": "unknown"
+									},
+									"defaultValue": "1"
+								}
+							],
+							"type": {
+								"type": "intrinsic",
+								"name": "unknown"
+							}
+						}
					]
				}
			],
[...]
		}
	],
[...]
}

Environment

• Typedoc version: ~0.22.12
• TypeScript version: ~4.6.2
• Node.js version: v16.14.0
• OS: Windows 11
• Related:
  • Comments are only present on the first method signature if multiple are defined #1879 - Jsdocs comments only present on first signature

[Gerrit0]

This is working as expected. The implementation signature is not visible to consumers of the function and is therefore not included in the documentation. You could create a plugin which extracts the information you need at conversion time.

const td = require("typedoc")

exports.load = function(app) {
  app.converter.on(td.Converter.EVENT_CREATE_DECLARATION, (context, reflection) => {
    // getSymbolFromReflection is marked @internal, in the next version with breaking changes
    // the symbol should be passed in to this listener so it shouldn't be necessary here
    const symbol = context.project.getSymbolFromReflection(reflection);
    if (!symbol) return;

    if (reflection.kindOf(td.ReflectionKind.Function | td.ReflectionKind.Method)) {
      console.log(symbol.declarations?.map(d => d.getText()))
    }
  });
}

[ST-DDT]

What would be the best way to get the complete default value from the implementation signature?

[Dayday10]

Has this issue been fixed?

[Gerrit0]

What would be the best way to get the complete default value from the implementation signature?

That's going to depend on what you mean by "complete". Default values are an arbitrary expression, there's no guarantee that they are a simple value... so it really depends on your use case. The simplest way to do this is, of course, to just get the text from the source file. This will put the default parameters in the JSON as strings from the source file, or null if a parameter doesn't have a default value.

// typedoc --plugin path/to/this/file.js
const td = require("typedoc");

/** @param {td.Application} app */
exports.load = function (app) {
    app.converter.on(
        td.Converter.EVENT_CREATE_DECLARATION,
        /**
         * @param {td.Context} context
         * @param {td.Reflection} reflection
         */
        (context, reflection) => {
            const symbol = context.project.getSymbolFromReflection(reflection);
            if (!symbol) return;

            if (
                reflection.kindOf(td.ReflectionKind.Function | td.ReflectionKind.Method) &&
                (symbol.declarations?.length ?? 0) > 1
            ) {
                const lastDeclaration = symbol.declarations[symbol.declarations.length - 1];
                if (td.TypeScript.isFunctionLike(lastDeclaration)) {
                    reflection.implementationDefaultParameters = lastDeclaration.parameters.map(
                        (param) => param.initializer?.getText() || null
                    );
                    console.log(reflection.implementationDefaultParameters);
                }
            }
        }
    );

    // So that it shows up in JSON output
    app.serializer.addSerializer({
        serializeGroup(item) {
            return item instanceof td.Reflection;
        },
        supports(item) {
            return true;
        },
        toObject(refl, obj) {
            obj.implementationDefaultParameters = refl.implementationDefaultParameters;
            return obj;
        },
    });
};

[ST-DDT]

Thanks for this example.
I added this to our project in faker-js/faker#656