Don't persist My Domain when using Welcome/Discovery login

[sfdctaka]

Summary

When an app uses a Welcome/Discovery domain (e.g., welcome.salesforce.com/discovery) as its login host, the domain discovery flow resolves the user's My Domain and passes it to handleCustomDomainUpdateWithLoginHint:. Previously, this called setLoginHost:, which persisted the My Domain into SFSDKLoginHostStorage and NSUserDefaults. This caused two problems:

1. The server picker list got polluted with My Domain entries
2. After logout, the login screen showed the My Domain instead of returning to the Welcome/Discovery page

Changes

• SFOAuthCoordinator: Remove setLoginHost: call from handleCustomDomainUpdateWithLoginHint:loginHint: — credentials.domain is sufficient for the auth flow and doesn't pollute persistent storage.
• SFUserAccountManager: Skip overwriting loginHost with credentials.domain when the current login host is a discovery domain (checked via DomainDiscoveryCoordinator.isDiscoveryDomain:).
• WelcomeDiscoveryLoginHostTests: Add tests covering isDiscoveryDomain logic, login host preservation after setting current user, and verifying storage isn't polluted.

Test Plan

• Unit tests pass (WelcomeDiscoveryLoginHostTests)
• Configure app with Welcome/Discovery domain → log in → verify login host remains discovery domain
• Log out → verify login screen returns to Welcome/Discovery page (not My Domain)
• Verify server picker does not accumulate My Domain entries after repeated login/logout cycles
• Verify non-discovery login flow still updates login host normally (regression check)

[github-actions]

	1 Warning
⚠️	Static Analysis found an issue with one or more files you modified. Please fix the issue(s).

Clang Static Analysis Issues

File	Type	Category	Description	Line	Col
SFOAuthCoordinator	Nullability	Memory error	nil assigned to a pointer which is expected to have non-null value	119	19
SFOAuthCoordinator	Nullability	Memory error	nil assigned to a pointer which is expected to have non-null value	243	15
SFUserAccountManager	Nullability	Memory error	Null passed to a callee that requires a non-null 2nd parameter	1579	15
SFUserAccountManager	Nullability	Memory error	Null passed to a callee that requires a non-null 2nd parameter	1594	15
SFUserAccountManager	Nullability	Memory error	nil passed to a callee that requires a non-null 2nd parameter	2232	13

Generated by 🚫 Danger

[github-actions]

	Tests	Passed ☑️	Skipped	Failed ❌️
SalesforceSDKCore iOS ^26 Test Results	638 ran	636 ✅		2 ❌

Test	Result
SalesforceSDKCore iOS ^26 Test Results
SFSDKAuthConfigUtilTests.testBrowserBasedLoginEnabled	❌ failure
SFUserAccountManagerTests.testUserAccountEncoding	❌ failure

• View SalesforceSDKCore iOS ^26 Test Results

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 68.20%. Comparing base (36f6bf6) to head (2459542).
⚠️ Report is 8 commits behind head on dev.

Additional details and impacted files

@@            Coverage Diff             @@
##              dev    #4046      +/-   ##
==========================================
- Coverage   70.61%   68.20%   -2.42%     
==========================================
  Files         245      245              
  Lines       21461    21461              
==========================================
- Hits        15155    14637     -518     
- Misses       6306     6824     +518     

Components	Coverage Δ
Analytics	70.78% <ø> (ø)
Common	70.69% <ø> (-0.19%)	⬇️
Core	61.66% <100.00%> (-3.74%)	⬇️
SmartStore	73.44% <ø> (ø)
MobileSync	88.79% <ø> (ø)

Files with missing lines	Coverage Δ
...lesforceSDKCore/Classes/OAuth/SFOAuthCoordinator.m	51.58% <ø> (-10.92%)	⬇️
...SDKCore/Classes/UserAccount/SFUserAccountManager.m	54.75% <100.00%> (-7.38%)	⬇️

... and 24 files with indirect coverage changes

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[github-actions]

	Tests	Passed ✅	Skipped	Failed
AuthFlowTester UI Test Results all	1 ran	1 ✅

Test	Result
No test annotations available

• View AuthFlowTester UI Test Results all

[github-actions]

	Tests	Passed ☑️	Skipped	Failed ❌️
SalesforceSDKCore iOS ^18 Test Results	638 ran	636 ✅		2 ❌

Test	Result
SalesforceSDKCore iOS ^18 Test Results
testMissingMyDomain()	❌ failure
SFSDKAuthConfigUtilTests.testBrowserBasedLoginEnabled	❌ failure

• View SalesforceSDKCore iOS ^18 Test Results

[bbirman]

nice finding a simple check!

[brandonpage]

LGTM, but before I approve I would like to know how/where the correct (My Domain) url gets saved on the user when they login with Welcome.

[sfdctaka]

LGTM, but before I approve I would like to know how/where the correct (My Domain) url gets saved on the user when they login with Welcome.

@brandonpage In line 870, self.credentials.domain = myDomain; of handleCustomDomainUpdateWithLoginHint:myDomain:, SFOAuthCoordinator holds onto self.credentials from start to finish. When domain discovery resolves mycompany.my.salesforce.com, it's written directly onto that credentials object.

When [self authenticate] is called immediately after, it reads credentials.domain to construct https://mycompany.my.salesforce.com/services/oauth2/authorize?..... No global loginHost needed.

After auth completes, finalizeAuthCompletion: → applyCredentials:withIdData: assigns authSession.oauthCoordinator.credentials (which still carries domain = mycompany.my.salesforce.com) to the user account, then calls saveAccountForUser: which archives it via NSCoding.