`dune init project` is broken due to project/workspace root detection

[shonfeder]

Expected Behavior

dune init proj foo should initialize a new project in the directory foo.

Actual Behavior

$ dune init proj foo
Error: I cannot find the root of the current workspace/project.
If you would like to create a new dune project, you can type:

    dune init project NAME

Otherwise, please make sure to run dune inside an existing project or
workspace. For more information about how dune identifies the root of the
current workspace/project, please refer to
https://dune.readthedocs.io/en/stable/usage.html#finding-the-root

A workaround is

$ touch dune-project
$ dune init proj foo

but, obviously, this is broken behavior.

Reproduction

I don't know how we can test this in our current CI/cram set up, since those all exist within a dune project.

Specifications

• Version of dune (output of dune --version): 3.0+alpha-867-gf22e56c
• Version of ocaml (output of ocamlc --version): version 4.11.1
• Operating system (distribution and version): Ubuntu 21.04

Must be because of #4921. The solution here should be to move root detection to later on in dune init. And in fact, dune init project should probably not detect the root at all given that it is creating a new project.

I don't know how we can test this in our current CI/cram set up, since those all exist within a dune project.

It's a bit tedious indeed. Dune detects when it is run from inside dune (via the environment variable INSIDE_DUNE) and behave differently. For instance, it disables root detection and use the current working directory as root. This is to avoid the inner dune scanning up the file system and picking up arbitrary files.

[shonfeder]

Sorry @bobot: afaict the breakage here is unrelated to any changes I made and I don't have the bandwidth to pick up the bug fix.

From my brief look, the root detection mechanism will need to non-trivial reworking. In order not to break the project initialization, the root detection in https://github.com/ocaml/dune/blob/main/bin/workspace_root.ml#L65-L94 will need some way of communicating an override that is determined after CLI parsing (afaik, since the parser is applicative, we don't have access to intermediate values until the entire command has been parsed).

[shonfeder]

dune init project should probably not detect the root at all given that it is creating a new project.

Dune init is only calling Common.term, but because the root detection is embedded in the parser for the common options, the root detection is forced upon it.

[bobot]

No problem, thanks for the analysis!