MBL-2658: Move design system code into new package named KDS by amy-at-kickstarter · Pull Request #2598 · kickstarter/ios-oss

amy-at-kickstarter · 2025-08-21T20:28:31Z

📲 What

Move our all our new design system code into a local Swift package, named KDS.

🤔 Why

Pulling out domain-specific code into separate packages should improve our build times, by flattening our (Very vertical) dependency structure.
Modularizing code forces us to think more carefully about the dependencies it requires, ultimately forcing us to make smarter decisions about class/method visibility and dependencies.
The design system is a neatly packaged set of features, so it is a great first candidate for this kind of modularization.
SPM packages are nifty and mean we don't need to individually define files in our Xcode project.

🛠 How

I learned some interesting things throughout this process - these are called out specifically in code comments.

👀 See

amy-at-kickstarter · 2025-08-21T22:00:19Z

+    )
+  ],
+  swiftLanguageModes: [
+    .v5


Specifically calling out this package as Swift 5.0 and iOS 16.0.

This seems inconsistent with the swift-tools-version: 6.0 at the top of the file (commented out). Can you explain why they should both be here or delete one of them?

Just kidding, that breaks on CircleCI! Somewhat confusing why there are two definitions in this file, but looks like it's necessary.

Weird! Thanks for trying though

amy-at-kickstarter · 2025-08-21T22:02:38Z

 }

-extension UIColor {
+public extension UIColor {


I went down a really deep rabbit hole of figuring out which methods (specifically around color generation) should be public, and which should not be.

It started when I made UIColor.hex internal to the KDS package. This was actually really nifty, because it automatically flagged the handful of places in the code where we're manually creating colors off of the design system! But then I went pretty deep trying to figure out how to handle these one-off color cases...and eventually I came around to just making the method public again.

I wanted to highlight this because it is a very powerful tool for enforcing code conventions - you can be really intentional about only exposing a small surface area from your package/library, in a way that we typically don't bother to do.

amy-at-kickstarter · 2025-08-21T22:03:50Z

+      }
+
+      var error: Unmanaged<CFError>?
+      CTFontManagerRegisterFontsForURL(fontURL as CFURL, .process, &error)


Spiffy trick I found for registering fonts. This meant we can remove the Fonts section from Info.plist.

amy-at-kickstarter · 2025-08-21T22:05:07Z

+
+      var error: Unmanaged<CFError>?
+      CTFontManagerRegisterFontsForURL(fontURL as CFURL, .process, &error)
+      assert(error == nil, "Error registering font: \(String(describing: error))")


I went down another rabbithole making sure asserts work as we expect - they do, in fact, run in debug builds, but are stripped from release builds.

It would be good to verify if this is because SPM inherits build flags from the target building the SPM module (in this case, Library), or if SPM automatically adds the flag to strip assertions.

You can add custom swift build flags to an SPM module, so it's not totally clear to me how the inheritance of flags works.

amy-at-kickstarter · 2025-08-21T22:06:08Z

    UIImageView.appearance(whenContainedInInstancesOf: [UITabBar.self])
      .accessibilityIgnoresInvertColors = true

+    InterFont.registerFont()


I believe we can now add this to Kickstarter-Framework-Tests and get our screenshot tests all building with Interfont.

amy-at-kickstarter · 2025-08-21T22:06:30Z

 import FBSDKCoreKit
 import Firebase
 import Foundation
+import KDS


Downside of modularization: 300 files that just add import KDS.

amy-at-kickstarter · 2025-08-21T22:06:57Z

    |> UITextField.lens.returnKeyType .~ .done
 }
-
-private let savePasswordButtonStyle: ButtonStyle = { button in


Unused, deleted because it required mixLighter which I made internal to KDS.

amy-at-kickstarter · 2025-08-21T22:07:20Z

-	<false/>
-	<key>GOOGLE_ANALYTICS_DEFAULT_ALLOW_AD_PERSONALIZATION_SIGNALS</key>
-	<false/>
-	<key>UIAppFonts</key>


See note above about fonts. Perhaps we should leave this line, though?

amy-at-kickstarter · 2025-08-21T22:09:15Z

               ReferencedContainer = "container:Kickstarter.xcodeproj">
            </BuildableReference>
         </TestableReference>
+         <TestableReference


This is one weird bit of SPM I can't quite figure out. I can add the KDS scheme, and we have a target KDSTests, but I can't just run KDSTests. Instead, I had to add them to another schema, in this case Library-iOS. I think this is because Xcode assumes an SPM module is an external dependency, and why would you want to test an external dependency all the time?

I'm not sure if there's a better workaround. Maybe using "Test Plans"? Thoughts welcome.

OK, I did figure this out. I had to add a schema to KDS, not to Kickstarter. You can now run the KDS tests from the Kickstarter project using CMD+U.

I still left this added to the Library schema, because I don't want to build a whole new CircleCI job just for these tests.

amy-at-kickstarter · 2025-08-21T22:09:43Z

 import UIKit

-// This extension contains custom semantic colors that are not part of the official Figma design set.
+// This extension contains custom semantic colors for PLOT that are not part of the official Figma design set.


These all are related to PLOT, so I rescoped them and left them in Library instead of KDS.

nativeksr · 2025-08-21T22:11:32Z

	1 Warning
⚠️	Big PR

Generated by 🚫 Danger

ifosli

Looks good! I have no suggestions for how to make things better (outside of the swift version comment) but I appreciate all your comments, as always!

ifosli · 2025-08-25T17:06:59Z

+    )
+  ],
+  swiftLanguageModes: [
+    .v5


This seems inconsistent with the swift-tools-version: 6.0 at the top of the file (commented out). Can you explain why they should both be here or delete one of them?

amy-at-kickstarter · 2025-08-28T14:54:50Z

            ReferencedContainer = "container:Kickstarter.xcodeproj">
         </BuildableReference>
      </MacroExpansion>
+      <EnvironmentVariables>


When you call Bundle.module, it looks for bundles inside the framework (like $(BUILT_PRODUCTS_DIR)/Library.framework/KDS_KDS.bundle). However, when you're building the framework alone (i.e. for tests), the bundle isn't copied there. By setting this environment variable in Debug, we can tell the compiler to look for the bundle in $(BUILT_PRODUCT_DIRS)/KDS_KDS.bundle instead.

This is necessary to keep our tests from crashing when you call Bundle.module.

ifosli · 2025-08-28T21:24:46Z

+    )
+  ],
+  swiftLanguageModes: [
+    .v5


Weird! Thanks for trying though

…are public

amy-at-kickstarter changed the title ~~[WIP] MBL-2658: Move design system code into new package named KDS~~ MBL-2658: Move design system code into new package named KDS Aug 21, 2025

amy-at-kickstarter commented Aug 21, 2025

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amy-at-kickstarter requested review from a team, ifosli, scottkicks and stevestreza-ksr and removed request for a team August 21, 2025 22:10

amy-at-kickstarter marked this pull request as ready for review August 21, 2025 22:10

ifosli approved these changes Aug 25, 2025

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amy-at-kickstarter changed the title ~~MBL-2658: Move design system code into new package named KDS~~ [WIP] MBL-2658: Move design system code into new package named KDS Aug 27, 2025

amy-at-kickstarter force-pushed the feat/adyer/mbl-2658/kds-spm branch from 09c105b to e86edc9 Compare August 27, 2025 17:43

amy-at-kickstarter changed the base branch from main to feat/adyer/mbl-2658/load-fonts-in-bundle August 27, 2025 17:44

amy-at-kickstarter commented Aug 28, 2025

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Base automatically changed from feat/adyer/mbl-2658/load-fonts-in-bundle to main August 28, 2025 15:49

amy-at-kickstarter changed the base branch from main to feat/adyer/mbl-2658/fix-hardcoded-colors August 28, 2025 17:26

amy-at-kickstarter force-pushed the feat/adyer/mbl-2658/kds-spm branch from 71724bc to 7c92cfa Compare August 28, 2025 17:26

amy-at-kickstarter changed the title ~~[WIP] MBL-2658: Move design system code into new package named KDS~~ MBL-2658: Move design system code into new package named KDS Aug 28, 2025

amy-at-kickstarter requested a review from ifosli August 28, 2025 17:28

amy-at-kickstarter force-pushed the feat/adyer/mbl-2658/fix-hardcoded-colors branch 2 times, most recently from ebc26ee to 0041ef7 Compare August 28, 2025 17:55

amy-at-kickstarter force-pushed the feat/adyer/mbl-2658/kds-spm branch from 7d00e20 to 75b297b Compare August 28, 2025 18:01

ifosli approved these changes Aug 28, 2025

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Comment thread KDS/Package.swift

)

],

swiftLanguageModes: [

.v5

ifosli Aug 28, 2025

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Weird! Thanks for trying though

Base automatically changed from feat/adyer/mbl-2658/fix-hardcoded-colors to main August 28, 2025 21:33

amy-at-kickstarter added 22 commits August 28, 2025 17:35

Create KDS package

e093881

Move base style files from Library into KDS

e18d144

Move UIColor hex + mixing utilities into KDS and mark as internal

363c73d

Run KDS tests as part of Library test target

c144c25

Import KDS in a lot of places

166743c

Add KDS xcode schema

276be87

Move CustomSemanticColors into Library and rename it PLOTSemanticColors

b124a7d

Rename NewDesignSystemColors.swift to Colors.swift

7ff9973

Rename UIColor.swift to UIColor+Hex.swift, tinker with which methods …

2a6a837

…are public

Remove some unused style code from FacebookResetPasswordViewController

60319aa

Change visibility of color methods

7b59b3d

Delete unused file KDS.swift

f50a27d

Move font resources from Library into KDS

69875a8

Add KDS as explicit dependency of Library

0d65c86

Make UIColor.hex private again, fix styles that didn't respect that

a4cc6e7

Move ColorsView into KDS

033006e

Fix tests

037a34f

Fix ColorsViewTests

b002d67

Delete extra KDS xcode scheme

06377e6

Change swift-tools-version to 5.0

0937dc1

Try swift tools 5.4

1766460

Set swift-tools-version back to 6.0

da4ddf4

amy-at-kickstarter force-pushed the feat/adyer/mbl-2658/kds-spm branch from 75b297b to da4ddf4 Compare August 28, 2025 21:37

amy-at-kickstarter merged commit c0f2489 into main Aug 28, 2025
5 checks passed

amy-at-kickstarter deleted the feat/adyer/mbl-2658/kds-spm branch August 28, 2025 21:52

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nativeksr commented Aug 21, 2025

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