fix: handling for empty cases in edge bundling

[mrstork]

Summary

These changes handle two empty cases

• The edge-function directory exists and is empty
• The edge-function directory exists and contains an empty manifest

Fixes FRB-1985

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[github-actions]

This pull request adds or modifies JavaScript (.js, .cjs, .mjs) files.
Consider converting them to TypeScript.

[serhalp]

by returning early, we're no longer recording these metrics (on line 152–153) with zeros. this might trigger some alerts or require some adjustments / context sharing. maybe we could avoid this change to keep things simple? and to allow tracking number of builds with no EFs

[pieh]

We also completely skip the entire step already of .netlify/edge-functions, netlify/edge-functions (or custom user one) and frameworks API one doesn't exist and don't report those metrics then.

This is overall similar scenario. We pondered about expanding current condition:

build/packages/build/src/plugins_core/edge_functions/index.ts

Lines 156 to 180 in 7782f6d

	// We run this core step if at least one of the functions directories (the
	// one configured by the user or the internal one) exists. We use a dynamic
	// `condition` because the directories might be created by the build command
	// or plugins.
	const hasEdgeFunctionsDirectories = async function ({
	buildDir,
	constants: { INTERNAL_EDGE_FUNCTIONS_SRC, EDGE_FUNCTIONS_SRC },
	packagePath,
	}): Promise<boolean> {
	const hasFunctionsSrc = EDGE_FUNCTIONS_SRC !== undefined && EDGE_FUNCTIONS_SRC !== ''
	if (hasFunctionsSrc) {
	return true
	}
	const internalFunctionsSrc = resolve(buildDir, INTERNAL_EDGE_FUNCTIONS_SRC)
	if (await pathExists(internalFunctionsSrc)) {
	return true
	}
	const frameworkFunctionsSrc = resolve(buildDir, packagePath || '', FRAMEWORKS_API_EDGE_FUNCTIONS_PATH)
	return await pathExists(frameworkFunctionsSrc)
	}

and try to find functions there already and skip entire step then, but it did feel a bit wasteful to repeat steps of trying to find edge functions multiple times and opted to do "early bail" inside step itself using edge functions search that we already do

[serhalp]

this results in a breaking change to the signature of the bundle() function exported from this package. if that's intentional, we should mark this PR as breaking (though note that since it changes two packages it'll cut a major for both).

(btw personal opinion but this is why I like https://typescript-eslint.io/rules/explicit-function-return-type/. it forces changes to return types to be explicit and visible.)

[mrstork]

Are you thinking this shouldn't be touched and we should only make the change on the adapter side of things? Just trying my best to understand what the way forward is that is being suggested.

[pieh]

Yeah, I think it make sense try not to touch edge-bundler and in particular change signature if possible here. I did take a look at how we handle this for serverless and we have similar early bail there, but it is in step itself instead of bundler/zisi and applied similar change in #6659 which is alternative to this PR - no breaking changes there and no additional file lookups