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    Once again, Daniel has great points. I would just like to add a few:

    • When documenting API’s, make sure to document preconditions and postconditions, as well an invariants.
    • Make sure to document guarantees and non-guarantees. Guarantees are things the code must or must not do, where non-guarantees are things that give the code wiggle room and which users cannot rely on, even if they begin to, a la https://xkcd.com/1172/.
    • Make sure docs can be tested, just like code. Daniel actually does this for curl docs (later in the post), but he does not list it as a standard. I think it’s a great way to help keep docs up to a high standard.
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      Admit it. If you browse around you will realize that the best documented projects you find never provide that docs generated directly from code.

      Is this saying that you shouldn’t use Javadoc or pydoc or “cargo doc”, where the documentation is located in the source files? So, from the previous point, it’s essential that docs live in the same repo as the code, but not the same files as the code? Seems like a pretty extreme position relative to the justification.

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        As a concrete example, Python’s official documentation is built using the Sphinx tool, and Sphinx supports extracting documentation from Python source files, but Python’s standard library documentation does not use it - the standard library does include docstrings, but they’re not the documentation displayed in the Standard Library Reference. Partially that’s because Python had standard library documentation before such automatic-documentation tools existed, but it’s also because the best way to organise a codebase is not necessarily the best way to explain it to a human.

        As another example in the other direction: Rust libraries sometimes include dummy modules containing no code, just to have a place to put documentation that’s not strictly bound to the organisation of the code, since cargo doc can only generate documentation from code.

        There’s definitely a place for documentation extracted from code, in manpage-style terse reference material, but good documentation is not just the concatenation of small documentation chunks.

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          Ah, I was thinking of smaller libraries, where you can reasonably fit everything but the reference part of the documentation on one (possibly big) page. Agreed that docs-from-code tools aren’t appropriate for big projects, where you need many separate pages of non-reference docs.

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          There’s definitely a place for documentation extracted from code, in manpage-style terse reference material, but good documentation is not just the concatenation of small documentation chunks.

          Can’t agree enough with this. Just to attempt to paint the picture a bit more for people reading this and disagreeing. Make sure you are thinking about the complete and exhaustive definition of ‘docs’. Surely you can get the basic API or stdlib with method arity and expected types and such, but for howtos and walkthroughs and the whole gamut it’s going to take some effort. And that effort is going to take good old fashioned work by technical folks who also write well.

          It’s taken me a long time to properly understand Go given that ‘the docs’ were for a long time just this and lacked any sort of tutorials or other guides. There’s been so much amazing improvement here and bravo to everyone who has contributed.

          On a personal note, the Stripe docs are also a great example of this. I cannot possibly explain the amount of effort or care that goes into them. Having written a handful of them myself, it’s very much “a lot of effort went into making this effortless” sort of work.

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            Yeah I hard disagree with that. The elixir ecosystem has amazing docs and docs are colocated with source by default for all projects, and use the same documentation system as the language.

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              Relevant links:

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              The entire D standard library documentation is generated from source code. Unittests are automatically included as examples. It’s searchable, cross-linked and generally nice to use. So yeah, I think this is just an instance of having seen too many bad examples of code-based docs and not enough good ones.

              When documentation is extracted from code in a language where that is supported well, it doesn’t look like “documentation extracted from code”, it just looks like documentation.

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                Check out Four Kinds of Documentation. Generated documentation from code comments is great for reference docs, but usually isn’t a great way to put together tutorials or explain broader concepts.

                It’s not that documentation generation is bad, just that it’s insufficient.

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                  Maybe the author is thinking about documentation which has no real input from the developer. Like an automated list of functions and arguments needed with no other contextual text.