Powershell: $ENV in using module

[MaynardMiner]

Summary of the new feature/enhancement

Using $ENV variables in using module statement

Proposed technical implementation details (optional)

My interest is to see the ability for using an environment variable for the using module statement:

using module $env:MY_DIR\build\module.psm1

The variables already exist prior to running powershell, and I imagine they have to be loaded prior to modules, so I would assume that such would be possible, but I am not sure how the back end works on this subject.

[SeeminglyScience]

The problem with this is that using module is a parse time concept. So that means:

1. Allowing the path to be dynamic would increase the time to parse the document, which greatly slows down editors. using module already makes parsing really slow, but it's worth mentioning
2. The variable would be evaluated at parse time, not runtime. That may not sound like a big deal in theory, but in practice it would feel really bad. That's part of why so few people even know about dynamic keywords, as a parse time only concept they feel terrible.

The variables already exist prior to running powershell, and I imagine they have to be loaded prior to modules, so I would assume that such would be possible, but I am not sure how the back end works on this subject.

They might exist, but they're not constants. They'll still be pulled on every request because you can change them at any point.

Also it's worth noting that you can use using module .\path\relative\to\file.psm1 and the . will work like $PSScriptRoot. Everything else in PowerShell uses that to refer to the current working directory except using statements.

[mburszley]

. will work like $PSScriptRoot

I didn't know that - not relative to $PWD like most other directory access? Given that it would cause a rewrite in how the parser works, I'm not sure the feature request adds anything.

[SeeminglyScience]

. will work like $PSScriptRoot

I didn't know that - not relative to $PWD like most other directory access?

Yup 🙂, except when using forward slashes due to a bug (#7424), then it's relative.

Super confusing, but tbh I'm not sure what else they could have done. Maybe treat PSScriptRoot and only PSScriptRoot as a constant, but 🤷‍♂ that'd be confusing too.

[mburszley]

except when using forward slashes due to a bug (#7424), then it's relative

I don't even know what to say. I'm surprised that's not a higher priority bugfix for 7.0 GA. To stay on-topic: I think you make good points for why this isn't feasible as it would make for a miserable authoring experience moving forward (although I've seen mixed adoption of the using statement in general due to knowing the nuances this deep)

[MaynardMiner]

I understand.

I've learned you can also use ..\path to get a parent, etc

Its just when you are writing different runtime scripts, and importing modules often, especially in different points of the program, and potentially while being in different directories- It gets hard to keep track of it. It's more of a convenience suggestion, if it was possible.

[mburszley]

@MaynardMiner If you need the dynamic behavior, I'd recommend sticking to Import-Module and importing your class definitions using Invoke-Expression to avoid the parse-time errors associated with PowerShell v5 classes.

[msftbot[bot]]

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