feat(experiment): add apps.icon.set support for non-hosted app icons by srtaalej · Pull Request #469 · slackapi/slack-cli

srtaalej · 2026-04-03T19:06:43Z

Changelog

No user-facing changes until apps.icon.set endpoint is live

Summary

This PR adds IconSet() API method targeting the apps.icon.set endpoint for non-hosted (Bolt) app icons. Gated behind the set-icon experiment flag (--experiment=set-icon) (see Note)

Expected Behavior / Test Plan

slack deploy → updateIcon() uses Icon() (no experiment needed, hosted apps, existing behavior)
slack deploy --experiment set-icon → updateIcon() uses IconSet() (both app types)
slack run --experiment set-icon → InstallLocalApp icon block runs via IconSet() (both app types)
slack run (no experiment) → no icon upload

Migration plan

When apps.icon.set is generally available:

Remove the set-icon experiment gate from updateIcon and InstallLocalApp
Replace all Icon() calls with IconSet()
Delete the deprecated Icon() method, its tests, mock, and the apps.hosted.icon constant

Note

🔴 The apps.icon.set endpoint is available under a toggle. No changes were made to the existing apps.hosted.icon flow.
Required scope (app_configurations:write) may be subject to change before the endpoint goes public

Requirements

I've read and understood the Contributing Guidelines and have done my best effort to follow them.
I've read and agree to the Code of Conduct.

codecov · 2026-04-03T19:09:08Z

Codecov Report

❌ Patch coverage is 26.08696% with 17 lines in your changes missing coverage. Please review.
✅ Project coverage is 71.15%. Comparing base (dd3d92e) to head (7b30774).

Files with missing lines	Patch %	Lines
internal/pkg/apps/install.go	0.00%	16 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #469      +/-   ##
==========================================
- Coverage   71.23%   71.15%   -0.08%     
==========================================
  Files         222      222              
  Lines       18664    18684      +20     
==========================================
  Hits        13295    13295              
- Misses       4189     4207      +18     
- Partials     1180     1182       +2

☔ View full report in Codecov by Sentry.
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zimeg

🐣 A few quick comments and questions and I'm excited to test this next!

internal/api/icon.go

internal/pkg/apps/install.go

Co-authored-by: Eden Zimbelman <zim@o526.net>

zimeg

@srtaalej Right now I'm not having luck with this when testing in a shared team sandbox and the error isn't so obvious to me...

Let me know if this is something perhaps with the image I use? I'll include it here for testing and other reviewers:

zimeg · 2026-04-07T23:46:42Z

internal/api/icon.go

 const (
 	appIconMethod = "apps.hosted.icon"
+	// appIconSetMethod is the API method for setting app icons for non-hosted apps.
+	appIconSetMethod = "apps.icon.set"


🔬 issue: This outputs a warning to verbose logs and it's not clear what I might not be including?

uploading icon icon error: https://slack.com/api/apps.icon.set error: missing_arguments Error updating app icon: https://slack.com/api/apps.icon.set error: missing_arguments Finished in 0.7s

are you uploading through the manifest or is the image just in the root of the project?

@srtaalej I saved this file to the root of the project 🌲 ✨

the "file" fielf for the api request had the wrong name! can you try again ?

zimeg

@srtaalej Woot! Thanks for finding these fixes! 📸

I'm approving now with a few notes of follow up that might be interesting. But testing so far is alright for me and fast enough on initial upload and re-uploads at ~4 seconds and ~2 seconds! Caching might not be an immediate concern perhaps? Notes:

The default "icon" field might be meaningful to add to the app manifest schema for developers with custom paths wanting editor hints?
The InstallLocalApp and the Install functions are now so similar enough to perhaps collapse into one function? Not urgent but it'd be a meaningful follow up to remove more from pkg internal 🎁

IMHO logging is important to land before this exits experiments but no blockers for this PR outside of note to document the experiment! 📚

zimeg · 2026-04-14T06:24:08Z

internal/pkg/apps/install.go

+			clients.IO.PrintDebug(ctx, "uploading icon")
+			_, iconErr := clients.API().IconSet(ctx, clients.Fs, token, app.AppID, iconPath)


🔬 question: Could we match debug log outputs for the apps.icon.set method here? Right now I find this in verbose:

uploading icon

While other methods include various request and response details that are useful in debugging. I think edges in image upload might make verbose logging most important here!

zimeg · 2026-04-14T06:39:02Z

internal/experiment/experiment.go

📚 note: Let's document this too!

https://docs.slack.dev/tools/slack-cli/reference/experiments

zimeg · 2026-04-14T06:40:01Z

internal/api/icon_test.go

 	require.NoError(t, err)
 }
+
+func TestClient_Icon(t *testing.T) {


🧪 praise: Thank you for updating existing tests to a familiar format!

zimeg · 2026-04-14T06:42:48Z

internal/api/icon.go

 	var part io.Writer
 	h := make(textproto.MIMEHeader)
-	h.Set("Content-Disposition", fmt.Sprintf(`form-data; name="%s"; filename="%s"`, "file", iconStat.Name()))
+	h.Set("Content-Disposition", fmt.Sprintf(`form-data; name="%s"; filename="%s"`, fileFieldName, iconStat.Name()))


Suggested change

h.Set("Content-Disposition", fmt.Sprintf(`form-data; name="%s"; filename="%s"`, fileFieldName, iconStat.Name()))

h.Set("Content-Disposition", fmt.Sprintf(`form-data; name="%s"; filename="%s"`, iconStat.Name()))

🌚 suggestion: Let's revert the addition of fileFieldName here and in arguments too if this is static?

feat: set icon method for Bolt apps

4d6a19e

srtaalej self-assigned this Apr 3, 2026

srtaalej added enhancement M-T: A feature request for new functionality experiment Experimental feature accessed behind the --experiment flag or toggle semver:patch Use on pull requests to describe the release version increment labels Apr 3, 2026

srtaalej and others added 2 commits April 6, 2026 12:34

test: add test coverage

2053f5d

Merge branch 'main' into ale-set-icon

febaece

srtaalej marked this pull request as ready for review April 6, 2026 22:56

srtaalej requested a review from a team as a code owner April 6, 2026 22:56

Merge branch 'main' into ale-set-icon

27ba074

srtaalej requested review from mwbrooks and zimeg April 7, 2026 17:07

zimeg reviewed Apr 7, 2026

View reviewed changes

internal/api/icon.go Outdated Show resolved Hide resolved

internal/api/icon.go Outdated Show resolved Hide resolved

internal/pkg/apps/install.go Outdated Show resolved Hide resolved

srtaalej and others added 4 commits April 7, 2026 14:36

Apply suggestions from code review

462e653

Co-authored-by: Eden Zimbelman <zim@o526.net>

linter

e11c382

Merge branch 'main' into ale-set-icon

e396a02

set-icon experiment restored

a126d2a

srtaalej requested a review from zimeg April 7, 2026 19:41

zimeg requested changes Apr 7, 2026

View reviewed changes

srtaalej and others added 3 commits April 8, 2026 14:12

change api field name

54387b6

Merge branch 'main' into ale-set-icon

b382d68

Merge branch 'main' into ale-set-icon

5d0ee94

srtaalej marked this pull request as draft April 10, 2026 19:58

srtaalej and others added 4 commits April 13, 2026 10:58

tests

4a06079

test

73e27f0

Merge branch 'main' into ale-set-icon

0c5b3be

clean up experiment gate

41a63f4

srtaalej marked this pull request as ready for review April 13, 2026 20:00

Merge branch 'main' into ale-set-icon

c5d8b54

Merge branch 'main' into ale-set-icon

7b30774

zimeg approved these changes Apr 14, 2026

View reviewed changes

		clients.IO.PrintDebug(ctx, "uploading icon")
		_, iconErr := clients.API().IconSet(ctx, clients.Fs, token, app.AppID, iconPath)

	h.Set("Content-Disposition", fmt.Sprintf(`form-data; name="%s"; filename="%s"`, fileFieldName, iconStat.Name()))
	h.Set("Content-Disposition", fmt.Sprintf(`form-data; name="%s"; filename="%s"`, iconStat.Name()))

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srtaalej commented Apr 3, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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Changelog

Summary

Expected Behavior / Test Plan

Migration plan

Note

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srtaalej commented Apr 3, 2026 •

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