Combining meta2json.py and rules.py into dromedary.py

[Release-Candidate]

Hi,

I've just combined these two scripts into a single one and before continuing and adding the generation of a opam switch I do have some questions regarding the use of these two scripts:

• Is the generation of the intermediate JSON output/input necessary for you at Facebook or can I drop it?
• The standard_library in the generated BUCK file: is this something that is needed by you and I should provide a command line switch for it, or can I always set it to ROOT/lib/ocaml
• I'd like to a config file which contains info about the Opam switch to create and packages to install in this switch as a first step, before using this newly generated switch as the current one. Is that ok for you? I'd make that part optional, only if such a config file is given as an argument to the script

See #1

[vsiles]

I'll have a look at the PR, thank you !
In the meantime:

• no, the json is not necessary, but it made designing and testing the scripts more easy. Not having to process the Opam switch all the time was quite nice. Also, as you mention, it could be improved to allow "sharing" of config to make more reproducible targets
• I'll leave @shayne-fletcher give more details, but it is something we'd like to keep as it is
• As long as you document the feature, I'm ok ;)

[shayne-fletcher]

The standard_library in the generated BUCK file: is this something that is needed by you and I should provide a command line switch for it, or can I always set it to ROOT/lib/ocaml

• I'll leave @shayne-fletcher give more details, but it is something we'd like to keep as it is

it appears we can always set it to ROOT/lib/ocaml sas suggested by @Release-Candidate.

i have pushed a change internally corresponding to facebook/buck2#442 that will soon make it's way into the facebook/buck2 repo that eliminates the standard_library symlink.

[Release-Candidate]

Thanks, great, one command line switch less.

A question: what is this resources supposed to contain as last entry? ROOT/lib/ocaml does not work for me.

 command_alias(
     name = "ocamldebug-exe",
     exe = ":ocamldebug",
     resources = [
         ":ocamlrun",
         ":ocamldebug",
         "_opam/lib/ocaml",
     ],

This is the relevant source line: https://github.com/facebook/ocaml-scripts/blob/main/rules.py#L396

I get an error when trying to use that in the BUCK file, removing the entry solves this error:

error: Error coercing attribute `resources` of `root//third-party:ocamldebug-exe`
      --> third-party/BUCK:38:1
       |
    38 | / command_alias(
    39 | |     name = "ocamldebug-exe",
    40 | |     exe = ":ocamldebug",
    41 | |     resources = [
    42 | |         ":ocamlrun",
    43 | |         ":ocamldebug",
    44 | |         "_opam/lib/ocaml",
    45 | |     ],
    46 | |     visibility = [
    47 | |         "PUBLIC",
    48 | |     ],
    49 | | ) if not host_info().os.is_windows else None
       | |_^
       |
    
    
    Error coercing attribute `resources` of `root//third-party:ocamldebug-exe`
    
    Caused by:
        0: Error coercing attribute `resources` of type `attrs.list(attrs.source(), default=[])`
        1: Error coercing [":ocamlrun", ":ocamldebug", "_opam/lib/ocaml"]
        2: Error coercing "_opam/lib/ocaml"
        3: Couldn't coerce `_opam/lib/ocaml` as a source.
             Error when treated as a target: Invalid absolute target pattern `_opam/lib/ocaml` is not allowed: Expected a `:`, a trailing `/...` or the literal `...`.
             Error when treated as a path: Expected file, but got a directory for path `_opam/lib/ocaml` in package `root//third-party`.

[vsiles]

I'm not the expert here, @shayne-fletcher do you remember ?
On our internal tool, we have a relative path path/to/lib/ocaml, relative to the location of the BUCK file. Does removing the _ works ? looks like it should be a relative path too from the location of the BUCK file to ocaml lib directory

[Release-Candidate]

Does removing the _ works ? looks like it should be a relative path too from the location of the BUCK file to ocaml lib directory

The path is ROOT/lib/ocaml and is correct, as I'm using a Opam sandbox in third-party directly without a symbolic link to opam, which also works after removing this line. But what I've just noticed, is that it works with a symlink, but not a directory.

So, if opam is a (sym-) link to ./_opam the BUCK config works. When I use the _opam directory directly, it does not.

Which means that the check for a directory does not treat a symlink to a directory as a directory, but as a file :). You might want to look into this, as that may cause real problems elsewhere. Well, actually not a symlink to a directory, but a relative path to a directory that starts with a symlink?!

[Release-Candidate]

That does not matter for dromedary.py, as it generates such a symlink to the Opam switch.

[vsiles]

For future reference, see most of the discussion happening in #1
@Release-Candidate thank you for your contribution !

[Release-Candidate]

You're welcome, glad I could help.

I've just started working on the config file to generate an Opam switch and install packages.