Add PORT env var to be used

[stramel]

Resolves #872

Changes

• Adds groundwork for allowing environment variables to be used by the CLI
• Keeps CLI Flags as priority over environment variables, based on this post (flag > envvar > config > default)
• Allows PORT environment variable to be used (PORT=4200 yarn dev)

Testing

Manually tested this by running the build and starting the cli directly from the astro.cjs file

Docs

I haven't updated this yet because I'm unsure where this information should live.

NOTE: I was attempting to set this up so we could easily support additional environment variables in the future without much effort. I could probably instead add just a simple change instead of the current PR like so:

-     port: typeof flags.port === 'number' ? flags.port : undefined,
+    port: typeof flags.port === 'number' ? flags.port : parseInt(PORT || '') || undefined,

So just let me know if I over-complicated it and I'll swap it out

[changeset-bot]

🦋 Changeset detected

Latest commit: cf5122e

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

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astro	Patch

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[natemoo-re]

Thanks so much for the contribution @stramel! I'm on board with this approach. Would you mind rebasing and marking this as ready for review?

[jasikpark]

lgtm, though i don't 100% get the types of everything 😅

would https://mael.dev/typanion/ be helpful or is it better to not pull in a whole dep for one task 😅?

[stramel]

I could definitely rewrite it with typanion if you would like. I will leave it up to you all

[stramel]

@FredKSchott did this break something? Saw it got reverted, just wondering if I need to fix something with this and re-issue a PR?

[FredKSchott]

Ah sorry, I got pulled away right after reverting. Check this thread out: https://discord.com/channels/830184174198718474/845430950191038464/875149362928443402

I also missed that PR though, and have some thoughts :) I might recommend doing this more flexibly via config, since that then sets any user up to do port: process.env.PORT in their config file. The reason is that PORT is very vague, and could already be set due to any number of other projects on the user's machine.

I know this isn't ideal way to leave this feedback (and I should have gotten it to you sooner) Happy to chat in literally any other venue (discord thread or RFC) if you'd like to keep discussing.