# Convert an extension into standalone application

**URL:** <https://discourse.slicer.org/t/convert-an-extension-into-standalone-application/23371>\
**Category:** Development\
**Tags:** build, extensions-manager\
**Created:** [May 11, 2022, 10:26am UTC](https://discourse.slicer.org/t/convert-an-extension-into-standalone-application/23371 "2022-05-11T10:26:21Z")\
**Posts on this page:** 1\
**Showing post:** 4

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**Author:** ![lassoan](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/lassoan/32/13_2.png) [@lassoan](https://discourse.slicer.org/u/lassoan)\
**Post date:** [May 12, 2022, 2:03am UTC](https://discourse.slicer.org/t/convert-an-extension-into-standalone-application/23371/4 "2022-05-12T02:03:05Z")

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The ` CMake variable EXTENSION_WC_REVISION is empty !` error is due to building an extension that is not under revision control. You can choose to either build the extension from a git version-controlled folder or specify the extension revision manually as described [here](https://discourse.slicer.org/t/3d-slicer-release-build-error-variable-slicer-wc-last-changed-date-is-expected-to-be-defined-in-slicerpackageanduploadtarget/20984/23).

While obviously developers must always use revision control, Slicer project should probably not enforce this as a mandatory rule. Therefore, I’ve submitted a pull request that changes the build error to just a warning:

> <https://github.com/Slicer/Slicer/pull/6365>
>
> Developers often complained that their extension build failed for some unknown r…eason and frequently the issue was that they did not store the source code in a git repository.
> 
> It is good to encourage developers to use best practices, such as version control, but making the build fail if they build from a non-version-controlled repository was unnecessarily strong measure.
> 
> This commit changes the behavior so that if an extension is built from a non-git folder then the build succeeds, just a warning is displayed during project configuration step and \`NA\` is used as the extension's WC revision.

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_[View the full topic](https://discourse.slicer.org/t/convert-an-extension-into-standalone-application/23371)._