feat: add request and response interceptors

[ddelgrosso1]

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Fixes #490 🦕

[ddelgrosso1]

Pinning compodoc because the downstream dep @angular-devkit/schematics appears to have dropped < Node 16 in the latest version which was breaking CI for us.

[danielbankhead]

Rather than adding GaxiosInterceptorType perhaps we can have separate methods for #applyInterceptors; #applyRequestInterceptors and #applyResponseInterceptors - the logic in #applyInterceptors can be cleanly separated by its if/else condition

[ddelgrosso1]

That was what I was originally trying to avoid but now that I think about it, makes more sense, single responsibility and all that. Will adjust.

[danielbankhead]

What are the benefits of GaxiosInterceptorManager over a Map? They are also ordered by insertion.

[ddelgrosso1]

I keep forgetting that JavaScript maps behave like that.

[ddelgrosso1]

The additional benefit of using a class is that we don't have to add functions to Gaxios.ts to add, remove, clear interceptors. It keeps things a bit more separated that way.

[ddelgrosso1]

Simplified the class to use maps under the hood. Kept it wrapped in a class just to keep the logic from seeping into Gaxios.ts

[danielbankhead]

Do we need an await here if we make the calls between request and the interceptor calls async?

Suggested change

	assert.rejects(instance.request({url}));
	assert.rejects(await instance.request({url}));

[ddelgrosso1]

I don't believe so assert.rejects will await the promise returning function.

[danielbankhead]

Looks great! One optional suggestion

[danielbankhead]

[completely optional]: Actually, I'm realizing a Set might be better here than a Map. Sets are also kept in insertion order and the API is 1:1:

• addInterceptor() -> add()
• removeInterceptor(number) -> delete(function) (might be easier for customers to find/remove)
• removeAll -> clear

Suggested change

	export class GaxiosInterceptorManager<
	T extends GaxiosOptions | GaxiosResponse,
	> {
	interceptorMap: Map<Number, GaxiosInterceptor<T> | null>;
	constructor() {
	this.interceptorMap = new Map<Number, GaxiosInterceptor<T>>();
	}
	/**
	* Adds an interceptor.
	*
	* @param {GaxiosInterceptor} interceptor the interceptor to be added.
	*
	* @returns {number} an identifier that can be used to remove the interceptor.
	*/
	addInterceptor(interceptor: GaxiosInterceptor<T>): number {
	const index = this.interceptorMap.size;
	this.interceptorMap.set(index, interceptor);
	return index;
	}
	/**
	* Removes an interceptor.
	*
	* @param {number} id the previously id of the interceptor to remove.
	*/
	removeInterceptor(id: number) {
	if (this.interceptorMap.has(id)) {
	this.interceptorMap.set(id, null);
	}
	}
	/**
	* Removes all interceptors.
	*/
	removeAll() {
	this.interceptorMap.clear();
	}
	}
	export class GaxiosInterceptorManager<
	T extends GaxiosOptions | GaxiosResponse,
	> extends Set<GaxiosInterceptor<T> | null> {}

And as feats are added to the Set we can get new stuff for free, like this handy difference method:

• https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Set/difference