# Trying to find out how pkg environment works

**URL:** <https://discourse.julialang.org/t/trying-to-find-out-how-pkg-environment-works/59582>\
**Category:** New to Julia\
**Tags:** question, environment\
**Created:** [April 19, 2021, 7:46am UTC](https://discourse.julialang.org/t/trying-to-find-out-how-pkg-environment-works/59582 "2021-04-19T07:46:39Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![quazirfan](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/quazirfan/32/23381_2.png) [@quazirfan](https://discourse.julialang.org/u/quazirfan)\
**Post date:** [April 19, 2021, 7:46am UTC](https://discourse.julialang.org/t/trying-to-find-out-how-pkg-environment-works/59582/1 "2021-04-19T07:46:39Z")

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If I see the following line after evaluating an use statement, such as `using MLJ` - does it mean I am using local git cloned copy?  
`[Info: Precompiling MLJ [add582a8-e3ab-11e8-2d5e-e98b27df1bc7]`  
(This is one a default environment.)

I have installed Revise.jl, and downloaded local copy of MLJ using pkg dev command, but that is on a separate environment. I am not sure how one environment can affect another.

Some clarification would help. Thanks!

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**Author:** ![hendri54](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/hendri54/32/9621_2.png) [@hendri54](https://discourse.julialang.org/u/hendri54)\
**Post date:** [April 20, 2021, 4:50pm UTC](https://discourse.julialang.org/t/trying-to-find-out-how-pkg-environment-works/59582/2 "2021-04-20T16:50:46Z")

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Your question is not quite clear (to me). But since there are no other takers, I’ll give it a try.

The `precompiling` message appears regardless of whether the package was added or developed.

Whether you are using the locally `dev`’d copy of `MLJ` or the one from the repo depends on the contents of the current environment’s `Project.toml`. It either points to a local path (`dev`) or to the repo (`add`).

As for the question whether one environment can affect another: you may be running into a stacked environment. If you first activate environment A and then B, the dependencies of both get merged (in other words, A’s dependencies are not forgotten when B is activated).

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**Author:** ![quazirfan](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/quazirfan/32/23381_2.png) [@quazirfan](https://discourse.julialang.org/u/quazirfan)\
**Post date:** [April 21, 2021, 7:00pm UTC](https://discourse.julialang.org/t/trying-to-find-out-how-pkg-environment-works/59582/3 "2021-04-21T19:00:57Z")

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Thanks. This talk was also helpful: [JuliaCon 2019 | Pkg, Project.toml, Manifest.toml and Environments | Fredrik Ekre - YouTube](https://www.youtube.com/watch?v=q-LV4zoxc-E)