refactor: move webview product and identity parsing to Swift

[nickolas-dimitrakas]

Background

Second slice of MPConvertJS: product and identity JSON parsing.

What Has Changed

• Added productFieldsFromJSON: and identityRequestFromJSON: to MPConvertJSFields.swift. 262 → 210 SLOC.
• Unlike promotion fields (refactor: move webview JSON field reading to Swift #929), product fields keep per-field if guards in the .m — MPProduct has nonnull string/number properties and a scalar position, so "absent" and "nil" aren't interchangeable here.
• Preserved: string prices coerce via -doubleValue (non-numeric strings → 0); position reads via -unsignedIntValue; product attributes require both key and value to be strings; a missing/non-array UserIdentities vs. a single malformed identity entry log and fail differently (the Swift result reports which); last-write-wins on duplicate identity types.
• Hardened: a non-dictionary entry in UserIdentities previously crashed (-[NSString objectForKeyedSubscript:]); now reports a malformed entry instead.

Validation

• abi-guard PASSED
• trunk check clean
• ObjC 1004 / Swift 650 tests green; new Swift coverage 21/21
• tvOS: CI only

Stack

Depends on #929.

Checklist

• Self-review completed
• Tests added or updated
• Tested locally

[github-actions]

🐦 Swift Migration Progress

Production implementation code at f5694a2110ad compared with 60c55d484d14.

Area	Goal	Progress	Base	This PR	Swift SLOC	Objective-C remaining	Change
Core SDK	Short term — in scope	█████▍░░░░	52.75%	53.29%	8,293	7,268	🚀 +0.54 pp
Core SDK	Long term — all Objective-C	███▉░░░░░░	38.38%	38.82%	8,293	13,071	🚀 +0.44 pp
SDK kit infrastructure	Short term — in scope	██████▊░░░	66.96%	66.96%	2,021	997	➖ 0.00 pp
SDK kit infrastructure	Long term — all Objective-C	████░░░░░░	39.95%	39.95%	2,021	3,038	➖ 0.00 pp
Standalone kits	Short term — in scope	▏░░░░░░░░░	1.06%	1.06%	152	14,218	➖ 0.00 pp
Standalone kits	Long term — all Objective-C	▏░░░░░░░░░	1.06%	1.06%	152	14,218	➖ 0.00 pp

Objective-C retained by design: Core SDK 5,803 · SDK kit infrastructure 2,041 · Standalone kits 0.

This PR's code movement

Area	Swift lines added	Objective-C lines removed
Core SDK	148	96
SDK kit infrastructure	0	0
Standalone kits	0	0

How this is measured

• Current composition uses production source lines of code (SLOC) from cloc; comments and blank lines are excluded.
• Short term — in scope excludes the Objective-C the migration will not delete, so 100% is the end of this project: every in-scope implementation gone.
• Long term — all Objective-C keeps the full denominator. Reaching 100% there means the public API itself becomes Swift, which is a breaking change reserved for a future major release.
• The gap between the two rows is the retained public/kit contract, runtime-identity, and boundary-glue surface listed in Tools/swift-migration-retained-objc.txt.
• Retained wrappers keep their Objective-C interface but still shed logic to Swift. That thinning moves the long-term row and the retained figure, not the short-term row.
• Both revisions are measured with the manifest from the head revision, so a manifest edit does not by itself move the reported change. A retained file this pull request renamed or deleted still counts as retained at the base.
• Pull request movement uses physical additions/deletions from git diff base...head --numstat; it counts retained files too and is intentionally separate from SLOC totals.
• Core excludes SDK kit infrastructure and vendored libraries. Standalone kits include only files below Kits/**/Sources.
• Tests, examples, headers, build outputs, vendored libraries, and the MParticle/Sources Swift overlay are excluded.
• Objective-C++ (.mm) is included in the Objective-C figures and removed counts.

Generated with cloc 2.10. This report is informational and does not gate migration direction.

[github-actions]

📦 SDK Size Impact Report

Measures how much the SDK adds to an app's size (with-SDK minus without-SDK).

Metric	Target Branch	This PR	Change
App Bundle Impact	2.48 MB	2.50 MB	+20 KB
Executable Impact	848 bytes	848 bytes	+N/A
XCFramework Size	6.82 MB	6.84 MB	+20 KB

➡️ SDK size impact change is minimal.

Raw measurements

Target branch (workstation/swift-migration):

{"baseline_app_size_kb":84,"baseline_executable_size_bytes":75464,"with_sdk_app_size_kb":2624,"with_sdk_executable_size_bytes":76312,"sdk_impact_kb":2540,"sdk_executable_impact_bytes":848,"xcframework_size_kb":6980}

This PR:

{"baseline_app_size_kb":84,"baseline_executable_size_bytes":75464,"with_sdk_app_size_kb":2644,"with_sdk_executable_size_bytes":76312,"sdk_impact_kb":2560,"sdk_executable_impact_bytes":848,"xcframework_size_kb":7000}

[cursor]

PR Summary

Medium Risk
Changes webview-driven product and identity parsing on a compatibility-sensitive path; behavior is largely preserved and tested, with one intentional hardening for malformed identity payloads.

Overview
Moves webview bridge parsing for products and identity API requests out of MPConvertJS.m into MPConvertJSFields, shrinking the Objective-C converter while keeping MPProduct / MPIdentityApiRequest construction in .m.

Swift adds productFieldsFromJSON: (optional fields, string price coercion via doubleValue, string-only attribute pairs) and identityRequestFromJSON: with typed outcomes (missingUserIdentities vs malformedEntry) so ObjC can still log only on a missing/non-array UserIdentities and return nil silently for a bad array entry. Identity pairs are applied in order with last-write-wins when the top-level Identity/Type duplicates a type from the array.

+product: and +identityApiRequest: now call those helpers; product assignment stays guard-based so absent JSON does not overwrite nonnull properties or assign position when the value is not an NSNumber.

Behavior fix: a non-dictionary element in UserIdentities no longer crashes; it is treated as a malformed entry. New unit tests cover product/identity edge cases.

^{Reviewed by Cursor Bugbot for commit f5694a2. Bugbot is set up for automated code reviews on this repo. Configure here.}