3 ms·

I'll give a shot at some guiding principals: 1. Do not use yaml. All github action logic should be written in a language that compiles to yaml, for example dh

I'll give a shot at some guiding principals: 1. Do not use yaml. All github action logic should be written in a language that compiles to yaml, for example dhall (https://dhall-lang.org/ https://dhall-lang.org/). Yaml is an awful language for programmers, and it's a worse language for non-programmers. It's good for no one. 2. To the greatest extent possible, do not use any actions which install things. For example, don't use 'actions/setup-node'. Use bazel, nix, direnv, some other tool to setup your environment. That tool can now also be used on your developer's machines to get the same versions of software as CI is using. 3. Actions should be as short and simple as possible. In many cases, they will be as simple as effectively "actions/checkout@v4", "run: ./ci/build.sh", and that's it. Escape from yaml as quickly as possible, put basic logic in bash, and then escape from bash as quickly as possible too into a real langauge. 4. Do not assume that things are sane or secure by default. Ideally you don't accept PRs from untrusted users, but if you do, read all the docs very carefully about what actions can run where, etc. Github actions on untrusted repos are a nightmare footgun.

eadmund 2y ago
> Escape from yaml as quickly as possible, put basic logic in bash, and then escape from bash as quickly as possible too into a real language. This should be your #1 rule. Don’t compile logic to YAML, just write it in a real language and call it as quickly as possible. This way a developer can run it from his workstation.
hnbad 2y ago
I agree with most of the points but I would condense #2 and #3 to "Move most things into scripts". Sometimes it's difficult to avoid complex workflows but generally it's a safer bet to have actual scripts you can re-use and use for other environments than GitHub. It's a bad idea to make yourself dependent entirely on one company's CI system, especially if it's free or an add-on feature. However I'd balk at the suggestion to use Dhall (or any equally niche equivalent) based on a number of factors: 1) If you need this advice, you probably don't know Dhall nor does anyone else who has worked or will work on these files, so everyone has to learn a new language and they'll all be novices at using that language. 2) You're adding an additional dependency that needs to be installed, maintained and supported. You also need to teach everyone who might touch the YAML files about this dependency and how to use it and not to touch the output directly. 3) None of the advice on GitHub Workflows out there will apply directly to the code you have because it is written in YAML so even if Dhall will generate YAML for you, you will need to understand enough YAML to convert it to Dhall correctly. This also introduces a chance for errors because of the friction in translating from the language of the code you read to the language of the code you write. 4) You are relying on the Dhall code to correctly map to the YAML code you want to produce. Especially if you're inexperienced with the language (see above) this means you'll have to double check the output. 5) It's a niche language so it's neither clear that it's the right choice for the project/team nor that it will continue to be useful. This is an extremely high bar considering the effort involved in training everyone to use it and it's not clear at all that the trade-off is worth it outside niche scenarios (e.g. government software that will have to be maintained for decades). It's also likely not to be a transferable skill for most people involved. The point about YAML being bad also becomes less of an issue if you don't have much code in your YAML because you've moved it into scripts.
- SOLAR_FIELDS 2y ago
  The other problem with Github Actions that I always mention that muddies the waters when it comes to discussions of it is that GHA itself is front loaded as actually multiple different things: 1. Event dispatching/triggers, the thing that spawns webhooks/events to do things 2. The orchestration implementation (steps/jobs, a DAG-like workflow execution engine) 3. The reusable Actions marketplace 4. The actual code that you are running as part of the build 5. The environment setup/secrets of GHA, in other words, the makeup of how variables and other configurations are injected into the environment. The most maintainable setups only leverage 1 directly from GHA. 2-5 can be ignored or managed through containerized workflow in some actual build system like Bazel, Nix, etc.
- michaelmior 2y ago
  You're also adding an extra build step that by its nature can't run in CI since it generates the CI pipelines. So now you need some way to keep your Dhall and YAML in sync. I suppose you could write one job in YAML that compiles the Dhall and fails the build if it's out of date, but it seems like a lot of extra work for minimal payoff. Instead, if you want to stay away from YAML, I'd say just move as much of the build as possible into external scripts so that the YAML stays very simple.
- JoelMcCracken 2y ago
  Not too long ago, I went down a rabbit hole of specifying GHA yaml via dhall, and quickly hit some problems; the specific thing I was starting with was the part I was frustrated with, which was the "expresssions" evaluation stuff. However, I quickly ran into the whole "no recursive data structures in dhall" (at least, not how you would normally think about it), and of course, a standard representation of expressions is a recursively defined data type. I do get why dhall did this, but it did mean that I quickly ran into super advanced stuff, and realized that I couldn't in good conscience use this as my team of mixed engineers would need to read/maintain it in the future, without any knowledge of how to do recursive definitions in dhall, and without the inclination to care either. an intro to this: https://docs.dhall-lang.org/howtos/How-to-translate-recursive-code-to-Dhall.html https://docs.dhall-lang.org/howtos/How-to-translate-recursiv... An example in the standard lib is how it works with JSON itself: https://store.dhall-lang.org/Prelude-v23.1.0/JSON/Type.dhall.html https://store.dhall-lang.org/Prelude-v23.1.0/JSON/Type.dhall... basically, to do recursive definitions, you have to lambda encode your data types, work with them like that, and then finally "reify" them with, like, a concrete list type at the end, which means that all those lambdas evaluate away and you're just left with list data. This is neat and intresting and worthy of learning, but would be wildly overly-complicated for most eng teams I think. After hitting this point in the search, I decided to go another route: https://github.com/rhysd/actionlint https://github.com/rhysd/actionlint and this project solved my needs such that I couldn't justify spending more time on it any longer.
michaelmior 2y ago
> To the greatest extent possible, do not use any actions which install things. Why not? I assume the concern is making sure development environments and production use the same configuration as CI. But that feels like somewhat of an orthogonal issue. For example, in Node.js, I can specify both the runtime and package manager versions using standard configuration. I think it's a bonus that how those specific versions get installed can be somewhat flexible.
- JoelMcCracken 2y ago
  To me, the issue comes when something weird is going on in CI that isn't happening locally, and you're stuck debugging it with that typical insanity. Yeah, it may be that you'll get the exact same versions of things installed, but that doesn't help when some other weird thing is going on. If you haven't experienced this, well, keep doing what you're doing if you want, but just file this reflection away for if/when you do hit this issue.
  - michaelmior 2y ago
    I've experienced this, but not often enough that it feels like a significant barrier.
rafram 2y ago
> All github action logic should be written in a language that compiles to yaml An imperative language that compiles to a declarative language that emulates imperative control flow and calls other programs written in imperative languages that can have side effects that change control flow? Please no.

eadmund 2y ago

> Escape from yaml as quickly as possible, put basic logic in bash, and then escape from bash as quickly as possible too into a real language. This should be your #1 rule. Don’t compile logic to YAML, just write it in a real language and call it as quickly as possible. This way a developer can run it from his workstation.

hnbad 2y ago

I agree with most of the points but I would condense #2 and #3 to "Move most things into scripts". Sometimes it's difficult to avoid complex workflows but generally it's a safer bet to have actual scripts you can re-use and use for other environments than GitHub. It's a bad idea to make yourself dependent entirely on one company's CI system, especially if it's free or an add-on feature. However I'd balk at the suggestion to use Dhall (or any equally niche equivalent) based on a number of factors: 1) If you need this advice, you probably don't know Dhall nor does anyone else who has worked or will work on these files, so everyone has to learn a new language and they'll all be novices at using that language. 2) You're adding an additional dependency that needs to be installed, maintained and supported. You also need to teach everyone who might touch the YAML files about this dependency and how to use it and not to touch the output directly. 3) None of the advice on GitHub Workflows out there will apply directly to the code you have because it is written in YAML so even if Dhall will generate YAML for you, you will need to understand enough YAML to convert it to Dhall correctly. This also introduces a chance for errors because of the friction in translating from the language of the code you read to the language of the code you write. 4) You are relying on the Dhall code to correctly map to the YAML code you want to produce. Especially if you're inexperienced with the language (see above) this means you'll have to double check the output. 5) It's a niche language so it's neither clear that it's the right choice for the project/team nor that it will continue to be useful. This is an extremely high bar considering the effort involved in training everyone to use it and it's not clear at all that the trade-off is worth it outside niche scenarios (e.g. government software that will have to be maintained for decades). It's also likely not to be a transferable skill for most people involved. The point about YAML being bad also becomes less of an issue if you don't have much code in your YAML because you've moved it into scripts.

SOLAR_FIELDS 2y ago
The other problem with Github Actions that I always mention that muddies the waters when it comes to discussions of it is that GHA itself is front loaded as actually multiple different things: 1. Event dispatching/triggers, the thing that spawns webhooks/events to do things 2. The orchestration implementation (steps/jobs, a DAG-like workflow execution engine) 3. The reusable Actions marketplace 4. The actual code that you are running as part of the build 5. The environment setup/secrets of GHA, in other words, the makeup of how variables and other configurations are injected into the environment. The most maintainable setups only leverage 1 directly from GHA. 2-5 can be ignored or managed through containerized workflow in some actual build system like Bazel, Nix, etc.
michaelmior 2y ago
You're also adding an extra build step that by its nature can't run in CI since it generates the CI pipelines. So now you need some way to keep your Dhall and YAML in sync. I suppose you could write one job in YAML that compiles the Dhall and fails the build if it's out of date, but it seems like a lot of extra work for minimal payoff. Instead, if you want to stay away from YAML, I'd say just move as much of the build as possible into external scripts so that the YAML stays very simple.
JoelMcCracken 2y ago
Not too long ago, I went down a rabbit hole of specifying GHA yaml via dhall, and quickly hit some problems; the specific thing I was starting with was the part I was frustrated with, which was the "expresssions" evaluation stuff. However, I quickly ran into the whole "no recursive data structures in dhall" (at least, not how you would normally think about it), and of course, a standard representation of expressions is a recursively defined data type. I do get why dhall did this, but it did mean that I quickly ran into super advanced stuff, and realized that I couldn't in good conscience use this as my team of mixed engineers would need to read/maintain it in the future, without any knowledge of how to do recursive definitions in dhall, and without the inclination to care either. an intro to this: https://docs.dhall-lang.org/howtos/How-to-translate-recursive-code-to-Dhall.html https://docs.dhall-lang.org/howtos/How-to-translate-recursiv... An example in the standard lib is how it works with JSON itself: https://store.dhall-lang.org/Prelude-v23.1.0/JSON/Type.dhall.html https://store.dhall-lang.org/Prelude-v23.1.0/JSON/Type.dhall... basically, to do recursive definitions, you have to lambda encode your data types, work with them like that, and then finally "reify" them with, like, a concrete list type at the end, which means that all those lambdas evaluate away and you're just left with list data. This is neat and intresting and worthy of learning, but would be wildly overly-complicated for most eng teams I think. After hitting this point in the search, I decided to go another route: https://github.com/rhysd/actionlint https://github.com/rhysd/actionlint and this project solved my needs such that I couldn't justify spending more time on it any longer.

michaelmior 2y ago

> To the greatest extent possible, do not use any actions which install things. Why not? I assume the concern is making sure development environments and production use the same configuration as CI. But that feels like somewhat of an orthogonal issue. For example, in Node.js, I can specify both the runtime and package manager versions using standard configuration. I think it's a bonus that how those specific versions get installed can be somewhat flexible.

JoelMcCracken 2y ago
To me, the issue comes when something weird is going on in CI that isn't happening locally, and you're stuck debugging it with that typical insanity. Yeah, it may be that you'll get the exact same versions of things installed, but that doesn't help when some other weird thing is going on. If you haven't experienced this, well, keep doing what you're doing if you want, but just file this reflection away for if/when you do hit this issue.
- michaelmior 2y ago
  I've experienced this, but not often enough that it feels like a significant barrier.

rafram 2y ago

> All github action logic should be written in a language that compiles to yaml An imperative language that compiles to a declarative language that emulates imperative control flow and calls other programs written in imperative languages that can have side effects that change control flow? Please no.