How do I affect the transpiled Kotlin when iterating on a skip module?

[tifroz]

I am new to skip, (evaluating Skip for a project)

As an experiment I put together a very simple skip app that uses skip-web, and, knowing I will have to make contributions to skip-web if I am going to use skip moving forward, I

• followed the directions for contributing to the skip-web project (https://skip.tools/docs/modules/skip-web/#contribution)
• made a small change to one of the swift files from skip-web (WebView.swift)
• built & tested against iOS (change was reflected) and Android emulator (change was NOT reflected)

I am just no sure where to go from there - my first reaction was to open the transpiled project in Android Studio so I followed the steps from https://skip.tools/docs/contributing/ for Working in Android Studio but after following the steps & recompiling the project, I still have no clue where the transpiled files for the customized skip-web module can be found and why the transpiled version is apparently unaffected by the code changes in WebView.swift.

Note that I did find WebView.kt under the project root's Android folder, but it looks like this code was generated from the original skip-web module, not from the customized module

Can anyone provide some pointers? Thanks in advance!

[marcprux]

So you have a workspace in Xcode that contains both your app as well as the skip-web package (as per https://skip.tools/docs/contributing/#local-libraries)? Any changes you make should certainly appear in your app when you build and run — this is how we develop Skip libraries ourselves.

What happens if you introduce a compile error in WebView.swift? Does it fail to build as expected?

Could you post a screenshot of the Xcode navigator window, as well as the contents of your Package.swift? There might be some simple issue that that might reveal.

[marcprux]

made a small change to one of the swift files from skip-web (WebView.swift)

BTW, what was the change that you made? Was is something that would be expected to appear in the transpiled Kotlin (i.e., not something gated by #if !SKIP)? skip-web has a lot of SKIP/non-SKIP branching logic, so is it possible that the part that you changed was something that was used only by the iOS side?

[marcprux]

Just for reference, here is what it looks like when I make a change to the Android part of the WebView implementation (changing the alpha to 0.5) and show it running in Showcase's WebViewPlayground example view.

[tifroz]

Thanks! You are right, I made changes inside an #if !SKIP block (I had introduced a new attribute scrollOffsetX on WebViewState, the value is updated at the same time when the existing attribute scrollingDown...it turns out that the scrollingDown attribute also never gets updated in Android). That explains that the changes did not affect the Android build

For future reference, how would one inspect / adjust the transpiled kotlin code from a local package? Following the documentation, I set the value of BUILT_PRODUCTS_DIR in Android/settings.gradle.kts:
System.setProperty("BUILT_PRODUCTS_DIR", "${System.getProperty("user.home")}/temp/xcodelocations/DerivedData/Project-cpanyjhzukgobjdmdypvqadyozxb/Build/Products/Debug-iphonesimulator")

I would have expected an Android or similar folder to show up under .../Build or under .../Build/Products after compiling successfully - but could not find anything suggesting that the kotlin projects had been generated there.

Can you help me figure out where to locate the kotlin project for inspection / debugging?

[marcprux]

The transpiled output will be visible through Xcode, but you usually need to follow the trick described at https://skip.tools/docs/debugging/#dual-platform-apps of selecting the "plugins" folder and changing its file type from "Folder" to "Folder" (due to a bug in Xcode in symbolic links). Once you do that, you can browse the transpiled Kotlin output either by digging through the folders under SkipStone/plugins/skip-web.output/…, or, more simply, with Xcode's quick open (CMD-OPTION-O) and enter, say, WebView.kt.

Note that you can view the output, but you can't change it. Instead, if you need to affect the generated Kotlin, either with code inside #if SKIP blocks, or using one of the other comment-based methods described at https://skip.tools/docs/platformcustomization/#skip-comments.

For example:

[tifroz]

Screen.Recording.2025-09-11.at.2.37.30.PM.mp4

I tried the plugins -> Folder trick, but no cigar (see video attachment). The website describes the ejectability feature, the ability to export a kotlin project transpiled by skip, and convert it into an independent Android Studio project. Does this process rely on the plugins trick you described?

(I am very grateful for the help!!)

[marcprux]

That's odd. What version of Xcode is this? After you change the drop-down to "Folder", then the "Type" field should disappear and the "plugins" link should start showing up as a folder.

if you click the little folder icon next to the Location reference, does it show you the a file system with a bunch of "package-name.output" folders?

[tifroz]

I am using Xcode Version 16.2 (16C5032a)

Attaching a screenshot of the folder content after clicking the Location Reference button

[marcprux]

I do recall there were some issues in 16.2 around the plugin outputs. Would it be possible to upgrade to Xcode 16.4 and see if the problem persists?

[tifroz]

Yes, it worked with Xcode 16.4! (For anyone else experiencing this, the expected folder hierarchy showed up under plugins after assigning the Folder type to plugins again + compiling the code with 16.4)