feat(create-gatsby): Add create-gatsby

[ascorbic]

This is a new command create-gatsby, which creates and configures a new site, a little like gatsby new on dexamethasone.

To run it:

npm init gatsby

or

yarn create gatsby

Goals

The command needs to run quickly, and get the user with a working site, configured to their needs, with a minumum number of steps.

The command aims to be as small as possible, because it has to download and install it before running. The target is <100kB, gzipped including dependencies. The current size is 75kB 95kB.

There should be no need for flags or arguments, because these are not easily discoverable. Instead it should use interactive configuration.

Architecture

To keep the install fast, the create-gatsby package does not depend on any gatsby packages except core-utils. When running, it uses enquirer to ask a number of questions to determine plugins to install. It starts by cloning and installing gatsby-starter-hello-world. It uses a stripped-down version of the initStarter command from gatsby-cli for this.

To install plugins it will use the copy of gatsby-cli in the newly-installed site. To do this, it resolves the gatsby-cli package relative to the site root, then loads create-cli. It then passes the plugin add args to that function, which runs it as if it had been invoked directly.

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[mxstbr]

This looks fantastic already! 😍

[mxstbr]

It would also be fantastic if we could already figure out how to automatically test this to ensure it works as expected. How we're going to best do that is honestly a bit of a questionmark in my head, I've never unit tested a CLI...

[ascorbic]

If we can work out how to do the interactive input we could test it by calling the run command, and mock execa so we can see what git commands it's trying to run.

[ascorbic]

Nice! https://medium.com/@zorrodg/integration-tests-on-node-js-cli-part-2-testing-interaction-user-input-6f345d4b713a

[ascorbic]

The mock-stdin package did the trick.

[gillkyle]

enquirer seems to have some internal logic to use the message if the name is falsy, so I just added a string to check against.

[ascorbic]

Haha. I was really confused this morning. I'd done literally the same fix yesterday but forgot to commit it. When I pulled it had already been changed, and I couldn't work out why it was still showing as uncommitted locally! Good solution 😉

[ascorbic]

I've disabled the tests until we can work out how to reproduce the failures

[mxstbr]

Small nits only, let's merge this into master?!

[KyleAMathews]

@ascorbic a bit late to the game but is there a reason this create call is awaited? It makes package installs serial — if you just return the promise, the NPMPackage provider will batch up all calls made at the same time into one npm/yarn install call.

[ascorbic]

@KyleAMathews Afaict, this should still work, because we're doing the calls to installPluginPackage in parallel in an async function. It will "await", but the async function will have already returned the promise so they'll still run in parallel

[KyleAMathews]

ahhh yeah 😅 async is hard. Carry on!

[ascorbic]

When it messes with my head, I find it helpful to think of an async function as starting with return new Promise...