staticFileContent like embedFile

[rubenmoor]

added function staticFileContent, allows embedding static assets as ByteString during compile time like embedFile does

I have:

• Based work on latest develop branch
• Followed the contribution guide
• Looked for lint in my changes with hlint . (lint found code you did not write can be left alone)
• Run the test suite: $(nix-build -A selftest --no-out-link)
• Updated the changelog
• (Optional) Run CI tests locally: nix-build release.nix -A build.x86_64-linux --no-out-link (or x86_64-darwin on macOS)

[fendor]

Hi!
Changes look good to me, I am just wondering what's the benefit here over using file-embed directly?

[rubenmoor]

Hi! Changes look good to me, I am just wondering what's the benefit here over using file-embed directly?

I can't use file-embed. embedFile :: FilePath -> Q Exp requires a FilePath which is, in case of a static asset, the result of template haskell code, too. I couldn't combine embedFile with staticFilePath because of the GHC stage restriction and figured, I can simply re-implement embedFile for static assets like I did in this PR.

I hope this makes sense. Maybe there is an alternative I overlooked.

[ali-abrar]

You should be able to produce the filepath without template haskell. It's just root </> fp, I believe.

[ali-abrar]

If you put a file in config/common or config/frontend, the contents are made available on the frontend. We do this by injecting the data as a base64-encoded string into the head of the page. You can use the functions in Obelisk.Configs to retrieve those configs. The decoding is handled for you via this interface.

Would this functionality serve your purposes here?

[cgibbard]

If I understand this change properly, it seems scary if the app has any large static files, no? If you were to drop, say, a 300MB video file into the static directory, emitting the entire contents of the video into your code at compile time might not work out too well. So if we want to do this, it should probably be controllable somehow. (But Ali's idea about using the existing config mechanism might also turn out to be good for your case here.)

[rubenmoor]

You should be able to produce the filepath without template haskell. It's just root </> fp, I believe.

There is the "asset pass through" mechanism, though. root </> someFilePath isn't aware of "static.out".

If you put a file in config/common or config/frontend, the contents are made available on the frontend. We do this by injecting the data as a base64-encoded string into the head of the page. You can use the functions in Obelisk.Configs to retrieve those configs. The decoding is handled for you via this interface.

Would this functionality serve your purposes here?

In principle, the config mechanism works. Only that my file isn't part of configuration in a meaningful way. I have a 770 kb file in json format that is the output of another haskell program, which I run prior to deployment. I.e. it contains expensively computed data that is then presented in the obelisk app.

Using the config mechanism just implies copying this file twice: to 'development-dir/config/frontend/' and to 'deployment-dir/config/frontend'. The internal base64 encoding and decoding is unnecessary overhead. (Given the efficiency of embedFile, which just reads the bytestring)

While feasible, I would consider this an abuse of the config mechanism.

[rubenmoor]

If I understand this change properly, it seems scary if the app has any large static files, no? If you were to drop, say, a 300MB video file into the static directory, emitting the entire contents of the video into your code at compile time might not work out too well. So if we want to do this, it should probably be controllable somehow. (But Ali's idea about using the existing config mechanism might also turn out to be good for your case here.)

It is just as scary as embedFile and given that, with obelisk and with this pull request, the file is shipped as part of the static file mechanism it is "controlled" like any other static file (images, videos, sounds, ...). You can check whether your app is too heavy on static files by checking the directory size. This is independent of how these files are embedded (in case of embedFile/this pull request that is as bytestrings).