nutgaard / typeanalyzer

Investigate datastructures

Type analyzer

A port of a similar library written in kotlin.

Useful in cases where you're not quite sure how a datastructure looks like, e.g whats nullable and whats not.

This library helps the investigation into what you can expect by capturing the structure, and generating examples classes for you.

Usage:

import {Typeanalyzer} from "./Typeanalyzer";

const serviceAnalyzer = new Typeanalyzer();

function somemethod(): Map<string, unknown> {
    const data = service.getSomeData();
    serviceAnalyzer.capture(data);
    return data;
}

NB: You should not reuse an instance of Typeanalyzer for objects you expect to be different.

Typeanalyzer captures and maintains an inner representation of the datastructures it has captures, which fields that are nullable, and what their types should be (See the representation in the snapshot).

To get the representation programmatically you can call serviceAnalyzer.report(), which returns the most up-to-date representation. This representation can be used to generate pseudo-code for kotlin and typescript:

const typescriptCode = serviceAnalyzer.print(new TypescriptFormat());
const kotlinCode = serviceAnalyzer.print(new KotlinFormat());

In-depth:

The typeanalyzer works by capturing the structure of a given value, and gradually relaxing the constraints.

F.ex;

const analyzer = new Typeanalyzer();
analyzer.capture(["value"]); // ListCapture[PrimitiveCapture[type = TEXT, nullable = false]]
analyzer.capture([null]);    // ListCapture[PrimitiveCapture[type = TEXT, nullable = true]]

If the typeanalyzer has not previously seen a valid type for a field, it tries to specify it if given the chance.

F.ex;

const analyzer = new Typeanalyzer();
analyzer.capture([null]);     // ListCapture[NullCapture[]]
analyzer.capture(["value"]);  // ListCapture[PrimitiveCapture[type = TEXT, nullable = true]]

In the previous example the analyzer was initally passed null in the first capture, and the specified field was thus marked as nullable. This is in contrast to if the analyzer has not yet seen any values in the list.

F.ex;

const analyzer = new Typeanalyzer();
analyzer.capture([]);         // ListCapture[UnknownCapture[]]
analyzer.capture(["value"]);  // ListCapture[PrimitiveCapture[type = TEXT, nullable = false]]
analyzer.capture([null]);     // ListCapture[PrimitiveCapture[type = TEXT, nullable = true]]