feat: change cy.intercept override behavior

[flotwig]

• Closes [Cypress 6.0.0] Overriding interceptors doesn't work. #9302
• Closes Implement response middleware pattern for net-stubbing #7788
• Closes cy.intercept / force404 #15209

User facing changelog

• BREAKING CHANGE: Request handlers supplied to cy.intercept are now matched starting with the most-recently-defined request interceptor. This allows users to override request handlers by calling cy.intercept again. This matches the previous behavior that was standard in cy.route.
• There are now new events on the req object for cy.intercept: before:response, response, after:response.
• Response handlers (supplied via event handlers or via req.continue(cb)) supplied to cy.intercept will be called in reverse order until res.send is called or until there are no more response handlers.
• A new option, middleware, has been added to the RouteMatcher type. If true, the supplied request handler will be called before any non-middleware request handlers.
• A new function, req.continue(cb), is available on request objects yielded by cy.intercept. It is functionally the same as req.reply(cb) - the request will stop propagating to other event handlers, will be sent outgoing, and the response will be handled by cb.
• cy.intercept can now be called with a new overload: cy.intercept(url, routeMatcher, handler). routeMatcher will be merged with url, and the handler is required.
• Fixed an issue where the response.body would be incorrect after stubbing a response using res.send({ fixture }) in a req.continue callback or a before:response or response handler.

Additional details

See changes to net_stubbing_spec for new + updated tests.

How has the user experience changed?

• New RouteMatcher option: middleware: boolean
  • Handlers with middleware: true will be called in the order they are defined and chained.
  • With middleware: true, only dynamic handlers are supported - makes no sense to support cy.intercept({ middleware: true }, staticResponse)
• req now emits events (regardless of middleware setting)
• Events on req:

  cypress/packages/net-stubbing/lib/external-types.ts

  Lines 207 to 226 in 762d6eb

  	interface InterceptionEvents {
  	/**
  	* Emitted before `response` and before any `req.continue` handlers.
  	* Modifications to `res` will be applied to the incoming response.
  	* If a promise is returned from `cb`, it will be awaited before processing other event handlers.
  	*/
  	on(eventName: 'before:response', cb: HttpResponseInterceptor): Interception
  	/**
  	* Emitted after `before:response` and after any `req.continue` handlers - before the response is sent to the browser.
  	* Modifications to `res` will be applied to the incoming response.
  	* If a promise is returned from `cb`, it will be awaited before processing other event handlers.
  	*/
  	on(eventName: 'response', cb: HttpResponseInterceptor): Interception
  	/**
  	* Emitted once the response to a request has finished sending to the browser.
  	* Modifications to `res` have no impact.
  	* If a promise is returned from `cb`, it will be awaited before processing other event handlers.
  	*/
  	on(eventName: 'after:response', cb: (res: CyHttpMessages.IncomingResponse) => void | Promise<void>): Interception
  	}

• req.continue(cb) has been added. req.reply(cb) still works.
• A third overload of cy.intercept has been added, to allow users to more easily do things like cy.intercept('/url', { middleware: true }, ...) to set middleware, etc:

  cypress/packages/net-stubbing/lib/external-types.ts

  Lines 459 to 470 in 042050c

  	/**
  	* Use `cy.intercept()` to stub and intercept HTTP requests and responses.
  	*
  	* @see https://on.cypress.io/intercept
  	*
  	* @example
  	* cy.intercept('/fruits', { middleware: true }, (req) => { ... })
  	*
  	* @param mergeRouteMatcher Additional route matcher options to merge with `url`. Typically used for middleware.
  	*/
  	intercept(url: string, mergeRouteMatcher: Omit<RouteMatcherOptions, 'url'>, response: RouteHandler): Chainable<null>
  	/**

PR Tasks

• Have tests been added/updated?
• Has the original issue or this PR been tagged with a release in ZenHub?
• Has a PR for user-facing changes been opened in cypress-documentation? docs: cy.intercept 7.0 changes cypress-documentation#3715
• Have API changes been updated in the type definitions?
• [na] Have new configuration options been added to the cypress.schema.json?

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[cypress]

---

Test summary

9497 • 0 • 111 • 3 • 0

---

Run details

Project	cypress
Status	Passed
Commit	ae33091
Started	Mar 26, 2021 5:21 PM
Ended	Mar 26, 2021 5:34 PM
Duration	12:06 💡
OS	Linux Debian - 10.8
Browser	Multiple

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---

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[kevinold]

@flotwig I think I have found a regression with this patch against the RWA with request modifications not being honored in some way.

In v6.6.0, when I remove the if-none-match header from a request (https://github.com/cypress-io/cypress-realworld-app/pull/676/files#diff-553f62c7d670ed3411a618d14b703ed95485dac575be4993025c3d263d099751R16-R18)

cy.intercept("GET", "/notifications", (req) => {
  delete req.headers["if-none-match"];
}).as("getNotifications");

Subsequent cy.wait's do not return a 304 from the endpoint

Under this branch, the response is 304 instead of the results:

[kevinold]

As of commit, c52133c

it broke this regular intercept for loginUser https://github.com/cypress-io/cypress-realworld-app/pull/676/files#diff-6c107e2390c5ad84e123f3be09d7b91ba35de8f8cc550d1f358c75806df47645R140-R148

[chrisbreiding]

LGTM 👍

[flotwig]

The 2 failing stages are currently failing in 7.0-release as well, merging.

[cypress-bot]

Released in 7.0.0.

This comment thread has been locked. If you are still experiencing this issue after upgrading to
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