prototype: Browser support Map<String,Object> (JS objects) in JSON codec

[laeubi]

Currently BrowserFunction/Evaluate only supports primitives and arrays but not objects.

This is a prototype to add support for having a Map<String, Object> support, but is not complete because Object/Map support is inconsistent across the 4 native backends because they use two different marshalling strategies:

┌────────────────────────┬────────────────────────────────────────────┬─────────────────────────────────────────┐
│ Backend                │ evaluate() return                          │ BrowserFunction args/return             │
├────────────────────────┼────────────────────────────────────────────┼─────────────────────────────────────────┤
│ Edge (win32)           │ via JSON.parse/stringify                   │ via JSON.parse/stringify                │
├────────────────────────┼────────────────────────────────────────────┼─────────────────────────────────────────┤
│ WebKitGTK              │ native jsc_value/JSValueRef walk (no JSON) │ via JSON.parse/stringify                │
├────────────────────────┼────────────────────────────────────────────┼─────────────────────────────────────────┤
│ Cocoa (legacy WebView) │ native WebScriptObject walk (no JSON)      │ native WebScriptObject walk (no JSON)   │
├────────────────────────┼────────────────────────────────────────────┼─────────────────────────────────────────┤
│ IE (win32 legacy)      │ native IDispatch/Variant walk (no JSON)    │ native IDispatch/Variant walk (no JSON) │
└────────────────────────┴────────────────────────────────────────────┴─────────────────────────────────────────┘

So  JSON.java  is only the actual conversion path for Edge (fully) and for WebKitGTK's  BrowserFunction  call marshalling (function args come in via a  swt://  URL query string that's JSON-encoded, and the return value is JSON-stringified back to JS). The other native paths inspect JS values directly (JSC API, WebScriptObject, IDispatch) and only ever check for arrays via a  length  property/index — no key enumeration exists for plain objects.

I still wanted to share this here for gathering feedback of others, if such partial support would be helpful (windows+linux) and possibly ideas how we can streamline this across different OS. My main workaround currently is to start a local webserver and using rest calls, but this is a bit brittle and not always possible due to restricted environments.

[github-actions]

Test Results

  212 files  ±0    212 suites  ±0   28m 51s ⏱️ + 1m 5s
4 894 tests ±0  4 870 ✅ ±0   24 💤 ±0  0 ❌ ±0 
7 065 runs  ±0  6 897 ✅ ±0  168 💤 ±0  0 ❌ ±0 

Results for commit 0108851. ± Comparison against base commit 4755f49.

[akurtakov]

Can you please add a snippet showing it?

[laeubi]

Can you please add a snippet showing it?

Showing what specifically? e.g. we have Snippet307 showing Browser Function usage.

[Copilot]

Copilot review overview

🔵 Needs a closer look

Backend-dependent public API behavior needs human compatibility review and regression validation.

Review effort: Balanced
Findings: 1 · 1

Open (2)

• Add regression tests for object and Map codec support · New
• Document object and Map support in public API Javadocs · New

What changed in this PR

Prototypes object/Map support in SWT’s shared browser JSON codec, without changing native conversion paths.

Changes:

• Decode JSON objects into insertion-ordered maps.
• Encode String-keyed maps, rejecting other key types.
• Document backend limitations internally.

File	Description
bundles/​org.eclipse.swt/​Eclipse SWT Browser/​common/​org/​eclipse/​swt/​browser/​JSON.java	Adds object/Map conversion and documents its scope.

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