Add `constants.EDGE_HANDLERS_DIST`

[ehmicky]

Some plugins have previously wanted to know the output directory where Functions are bundled. We provide with a non-configurable constants.FUNCTIONS_DIST for this purpose.

We might have the same need for Edge handlers. At the moment, the output directory is hard-coded as .netlify/edge-handlers. However, we probably should follow the same pattern and expose it as a non-configurable constants.EDGE_HANDLERS_DIST instead so Build plugins can use this value.

@mraerino @calavera @shortdiv What do you think?

[shortdiv]

I really like this idea! I think considering that users will be able to configure the edge handlers directory and user edge handler plugins will build to that directory, we'd want this capability

[ehmicky]

Done at #1830

[mraerino]

somehow i missed this specific issue. so sorry for being late to the party.

comment from the PR:

i have a strong opinion that this constant should be the choice of the plugin, not of netlify-build.
we are using that constant in other contexts like

• uploading handlers from CLI
• running handlers locally via traffic mesh

it doesn't make sense to move setting this to netlify-build. it's not something we consider good to use by anyone from the outside right now

[mraerino]

why is this different from functions?

we have a specific bundling format that is not openly documented and relies on a bunch of implementation details in our runtime. third parties won't be able to produce meaningful output into this directory

[ehmicky]

Yes, this makes sense, especially your last argument. Thanks for chiming in before we ship this.

My only concern would be if some Plugins started to reverse engineer .netlify/edge-handlers bundles and their contents. They would then hard-code the directory location. However, this can arguably be considered a hack, and we could prevent it during plugins code review.
Based on this, I agree we should close this issue. What do you think @shortdiv?

[mraerino]

yeah, we don't have to support hacks. that's the good thing about not providing this path openly

[erezrokah]

• uploading handlers from CLI

I would actually prefer if this was exposed in some way and not hardcoded in the CLI.
Also, @ehmicky do we need to resolve the path based on the site root here:
https://github.com/netlify/netlify-plugin-edge-handlers/blob/a9f8b0b11a1a476876966310a04ecc7acb051701/src/consts.js#L3
?

Using the plugin as a direct dependency in the CLI feels odd and I'm not sure it's worth separating that logic into a separate package just for the sake of exporting some consts.

[ehmicky]

I personally don't have any strong preference either way, so will let @mraerino and @shortdiv chime in.

Also, @ehmicky do we need to resolve the path based on the site root here: netlify/netlify-plugin-edge-handlers@a9f8b0b/src/consts.js#L3?

Yes, this is relative to the build directory (called this.api.site.root in the CLI).

[ehmicky]

While writing the documentation, the following potential use case was brought up: users might want to debug Edge handlers bundling by viewing the output bundles. This would require knowledge and documentation of .netlify/edge-handlers/. I don't know whether this is a good idea, but thought this belonged to this discussion.

[mraerino]

we don't need it right now, but we can keep it in the backlog for when people run into issues with the process