When JSON responses come back, they are sometimes not in the format expected by the API. As a result we have a lot of defensive coding (expressions like `(data || {}).someProperty`) to avoid exceptions being thrown in badge processing. Often we rely on the `try` blocks that wrap so much of the badge-processing code, which catch all JavaScript exceptions and return some error result, usually **invalid**. The problem with this is that these `try` blocks catch all sorts of programmer errors too, so when we see **invalid** we don't know whether the API returned something unexpected, or we've made a mistake. We also spend a lot of time writing defensive tests around malformed responses, and creating and maintaining the defensive coding.
A better solution is to validate the API responses using declarative contracts. Here the programmer says exactly what they expect from the API. That way, if the response isn't what we expect we can just say it's an **invalid json response**. And if our code then throws an exception, well that's our mistake; when we catch that we can call it a **shields internal error**. It's also less code and less error-prone. Over time we may be confident enough in the contracts that we won't need so many tests of malformed responses. The contract doesn't need to describe the entire response, only the part that's needed. Unknown keys can simply be dropped, preventing unvalidated parts of the response from creeping into the code. Checking what's in our response before calling values on it also makes our code more secure.
I used Joi here, since we're already using it for testing. There may be another contracts library that's a better fit, though I think we could look at that later.
Those changes are in base.js.
The rest is a rewrite of the remaining NPM badges, including the extraction of an NpmBase class. Inspired by @chris48s's work in #1740, this class splits the service concerns into fetching, validation, transformation, and rendering. This is treated as a design pattern. See the PR discussion for more. There are two URL patterns, one which allows specifying a tag (used by e.g. the version badge `https://img.shields.io/npm/v/npm/next.svg`), and the other which does not accept a tag (e.g. the license badge `https://img.shields.io/npm/l/express.svg`). Subclasses like NpmLicense and NpmTypeDefinitions can specify the URL fragment, examples, the validation schema for the chunk of the package data they use, and a render function. The NpmVersion subclass uses a different endpoint, so it overrides the `handle` implementation from NpmBase.
The remaining services using BaseJsonService are shimmed, so they will keep working after the changes.
* allow services to export >1 classes
This change to loadServiceClasses() allows us to define
services which either export a single service class e.g:
module.exports = class Cdnjs extends BaseService {
//...
}
or more than one. e.g:
module.exports = {
GemVersion,
GemDownloads,
GemOwner,
GemRank,
}
* refactor ruby gem badges
- move badge code to service classes
- throw exceptions for errors
- use let and const
- change tests to expect 'downloads' label for error badges
- general tidying
* fix typo in tests
* Don't always use class name in example label
This allows (for example) GemVersion and GemDownloads
both to use the example label 'Gem'
