Raising an error when an asset is not found

[tiagobabo]

As per the Rails docs, if one is using sprockets-rails >= 3.2.0 it's possible to set config.assets.unknown_asset_fallback = false and raise an error when an asset is not found. Looking at the current implementation of asset_url we get a warning if propshaft is unable to resolve an asset URL. Would it be possible to have a similar configuration that would allow raising an error instead (especially on assets:precompile)?

[rmacklin]

It's worth noting that propshaft already does raise a MissingAssetError for assets that aren't resolved when the asset is referenced directly in an actionview helper method like javascript_include_tag, etc., as seen here:

propshaft/lib/propshaft/helper.rb

Lines 3 to 5 in 62476fa

	def compute_asset_path(path, options = {})
	Rails.application.assets.resolver.resolve(path) || raise(MissingAssetError.new(path))
	end

The code linked in @tiagobabo's post is specific to assets that are referenced in a url(...) value within a CSS file, which are potentially transformed by the CssAssetUrls processor.

Note, however, that some expressions inside url() should never be transformed (e.g. an inline data-URI or a fully qualified URL to an external domain). This explains why the current implementation (of not raising an error) can be useful.

I do see the value in adding such a configuration to throw an exception rather than just logging a warning if an asset inside url() can't be resolved, but it seems like it would have to be restricted to only apply for expressions inside url() that makes sense to be transformed (e.g. relative URLs).

[tiagobabo]

You're right, this only happens for assets required inside url(...), thanks for clarifying that.

[brenogazzola]

My original implementation was for a raise, but when I started migration my own app from sprockets to propshaft, I noticed that it was easier to let all errors to be logged and fix them in batches than doing the crash-fix-reload-crash-fix-reload cycle.

Is there a reason why raising would be better? I'm asking because between our two experiences we might figure out a third option that might be better than logging/raising

[brenogazzola]

I’ll close this issue for now as it’s not a bug but a feature request, and from my experience logging provides a better workflow than raising. If anyone has further input, feel free to comment.