# How do i know my package is reading the correct \`Project.toml\` files?

**URL:** <https://discourse.julialang.org/t/how-do-i-know-my-package-is-reading-the-correct-project-toml-files/33499>\
**Category:** General Usage\
**Created:** [January 17, 2020, 6:05pm UTC](https://discourse.julialang.org/t/how-do-i-know-my-package-is-reading-the-correct-project-toml-files/33499 "2020-01-17T18:05:29Z")\
**Posts on this page:** 9\
**Page:** 1

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**Author:** ![affans](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/affans/32/11911_2.png) [@affans](https://discourse.julialang.org/u/affans)\
**Post date:** [January 17, 2020, 6:05pm UTC](https://discourse.julialang.org/t/how-do-i-know-my-package-is-reading-the-correct-project-toml-files/33499/1 "2020-01-17T18:05:29Z")

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I have developed a package `MyPackage` that has it’s own `Project.toml` and `Manifest.toml` files. I’ve `dev` this from my main environment so that my `v1.2 Project.toml` file looks like this:

```julia
(v1.2) pkg> st
    Status `~/.julia/environments/v1.2/Project.toml`
  [3c78c848] MyPackage v0.1.0 [`~/.julia/dev/mmrvaccinedelay`]

```

This allows me to do `using MyPackage` and everything works beautifully. `MyPackage` has the following code in it

```julia
module MyPackage

using DataFrames
using CSV
# module code
end

```

Both `DataFrames` and `CSV` exists in the project’s `Project.toml` file (but they also exist in the `v1.2 Project.toml` file). The question is, which one does my package look at. i.e. when I type in `using MyPackage` from the **main v1.2 environment** , does the package use `DataFrames, CSV` from the `v1.2 Project.toml` or the package’s own `Project.toml`.

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**Author:** ![fredrikekre](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/fredrikekre/32/1688_2.png) [@fredrikekre](https://discourse.julialang.org/u/fredrikekre)\
**Post date:** [January 17, 2020, 9:03pm UTC](https://discourse.julialang.org/t/how-do-i-know-my-package-is-reading-the-correct-project-toml-files/33499/2 "2020-01-17T21:03:47Z")

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> [@affans](#):
>
> The question is, which one does my package look at. i.e. when I type in `using MyPackage` from the **main v1.2 environment** , does the package use `DataFrames, CSV` from the `v1.2 Project.toml` or the package’s own `Project.toml` .

The one from the main v1.2 environment.

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**Author:** ![affans](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/affans/32/11911_2.png) [@affans](https://discourse.julialang.org/u/affans)\
**Post date:** [January 17, 2020, 9:53pm UTC](https://discourse.julialang.org/t/how-do-i-know-my-package-is-reading-the-correct-project-toml-files/33499/3 "2020-01-17T21:53:32Z")

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So what’s the purpose of the project having it’s own environment files? How do I force it so that when someone runs `using MyPackage`, all the dependencies of `MyPackage` are pulled from the `Project.toml` file instead of the main environment (or whatever other environment) the use user is in.

If I am understanding this correctly, whenever a `using xxx` statement is run, it will look for the package based on the `Project.toml` of the current user environment?

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**Author:** ![Tamas\_Papp](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/tamas_papp/32/25949_2.png) [@Tamas\_Papp](https://discourse.julialang.org/u/Tamas_Papp)\
**Post date:** [January 18, 2020, 4:46pm UTC](https://discourse.julialang.org/t/how-do-i-know-my-package-is-reading-the-correct-project-toml-files/33499/4 "2020-01-18T16:46:22Z")

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> [@affans](#):
>
> How do I force it so that when someone runs `using MyPackage` , all the dependencies of `MyPackage` are pulled from the `Project.toml`

You mean the versions? You are looking for [compat bounds](https://julialang.github.io/Pkg.jl/dev/compatibility/).

> [@affans](#):
>
> whenever a `using xxx` statement is run, it will look for the package based on the `Project.toml` of the current user environment?

Yes, the _active_ environment. See

[https://julialang.github.io/Pkg.jl/dev/environments/](https://julialang.github.io/Pkg.jl/dev/environments/)

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<div class="post-metadata">

**Author:** ![affans](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/affans/32/11911_2.png) [@affans](https://discourse.julialang.org/u/affans)\
**Post date:** [January 18, 2020, 5:32pm UTC](https://discourse.julialang.org/t/how-do-i-know-my-package-is-reading-the-correct-project-toml-files/33499/5 "2020-01-18T17:32:40Z")

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So when someone uses my package (`add`, `using MyPackage`), the user has to be in the `MyPackage` env for the correct packages to be pulled? For example, the `DataFrames` package version used in my `MyPackage` Project.toml file is slightly different than what most people would have in their updated `1.3` environment.

How can I ensure that `Pkg` pulls the older version that my package requires, without the user manually switching environments?

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**Author:** ![oxinabox](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/oxinabox/32/206603_2.png) [@oxinabox](https://discourse.julialang.org/u/oxinabox)\
**Post date:** [January 18, 2020, 9:54pm UTC](https://discourse.julialang.org/t/how-do-i-know-my-package-is-reading-the-correct-project-toml-files/33499/6 "2020-01-18T21:54:49Z")

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When you run `Pkg> add`  
then the package manager determines which version of your package and of its dependencies to add to the enviroment such that none of the the compat bounds of the users current enviroment or any package in there are violated.

Generally one of the advantages of not working in the global enviroment is that you don;t have a million different packages with a million different bounds all fighting about what shold be used.  
Thats why I advise everyone to have 1 enviroment per conceptual project.  
And to keep the global enviroment just for a few very commonly used tools.

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<div class="post-metadata">

**Author:** ![affans](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/affans/32/11911_2.png) [@affans](https://discourse.julialang.org/u/affans)\
**Post date:** [January 19, 2020, 3:09pm UTC](https://discourse.julialang.org/t/how-do-i-know-my-package-is-reading-the-correct-project-toml-files/33499/7 "2020-01-19T15:09:38Z")

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Something isn’t making sense to me for some reason.

It seems that the ideal workflow for anyone using my package is to create a new environment, and then do `add MyPackage, using MyPackage` from that environment which will pull dependencies based on the project’s `Project.toml` file.

What happens when the user does `add MyPackage, using MyPackage` from their `v1.3` environment, which is likely the case with many users? How does Pkg determine what versions of the dependencies to download? For example, `MyPackage` has `using DataFrames` and a particular version of `DataFrames` in the `Project.toml` file?

1. Which version of `DataFrames` is downloaded and used within the package? Is it the version that’s inside the project’s `Project.toml` file? Or is it the version that’s inside the active environment `Project.toml` (according to @fredrikekre, the answer is active, in this case `v1.3`).

1. Follow up if the answer above is “active”: Suppose the user dosn’t have `DataFrames` in their active environment. Since my `MyPackage` is calling `using DataFrames`, how will Pkg know which version of `DataFrames` to download?

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**Author:** ![GunnarFarneback](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/gunnarfarneback/32/1827_2.png) [@GunnarFarneback](https://discourse.julialang.org/u/GunnarFarneback)\
**Post date:** [January 19, 2020, 4:06pm UTC](https://discourse.julialang.org/t/how-do-i-know-my-package-is-reading-the-correct-project-toml-files/33499/8 "2020-01-19T16:06:26Z")

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> [@affans](#):
>
> For example, `MyPackage` has `using DataFrames` and a particular version of `DataFrames` in the `Project.toml` file?

No, there are no particular versions of the dependencies in the `Project.toml` file. Particular versions can be found in the `Manifest.toml` file.

The general idea is that `Project.toml` lists the dependencies and compatibility bounds (`compat` section) for which versions will work with your package. When someone adds your package to one of their environments, it’s the responsibility of the Pkg resolver to find dependency versions that work with _all_ the packages in the environment and download those. If the packages in the environment have contradictory compatibility requirements it will refuse to add your package.

> [@affans](#):
>
> It seems that the ideal workflow for anyone using my package is to create a new environment, and then do `add MyPackage, using MyPackage` from that environment which will pull dependencies based on the project’s `Project.toml` file.

Yes and no. It will pull the list of dependencies from your `Project.toml` file, and in the absence of other packages with different requirements will resolve the versions to the highest available versions (\*) that are consistent with your `compat` bounds.

In order to replicate exactly the same environment, what you should do is to commit both `Project.toml` and `Manifest.toml`, then instruct the user to activate your package (`Pkg.activate` or start with `--project`) and `Pkg.instantiate` to download the specific dependency versions found in `Manifest.toml`.

(\*) I hope I’m right on that detail. Otherwise someone will have to correct me.

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<div class="post-metadata">

**Author:** ![affans](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/affans/32/11911_2.png) [@affans](https://discourse.julialang.org/u/affans)\
**Post date:** [January 19, 2020, 10:14pm UTC](https://discourse.julialang.org/t/how-do-i-know-my-package-is-reading-the-correct-project-toml-files/33499/9 "2020-01-19T22:14:46Z")

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> [@GunnarFarneback](#):
>
> The general idea is that `Project.toml` lists the dependencies and compatibility bounds ( `compat` section) for which versions will work with your package. When someone adds your package to one of their environments, it’s the responsibility of the Pkg resolver to find dependency versions that work with _all_ the packages in the environment and download those. If the packages in the environment have contradictory compatibility requirements it will refuse to add your package.

Thank you. This was the explanation that really tied it all together for me. Now I know how to package my scientific projects as well as use `DrWatson.jl` to manage everything.