In several places we do awkward things like the following since we can't directly test protocol version or supported features. // COMPATIBILITY (iOS 9): Legacy backends don't support breakpoint ignore count. Since support // can't be tested directly, check for CSS.getSupportedSystemFontFamilyNames. if (CSSAgent.getSupportedSystemFontFamilyNames) { In cases where we can't use Agent.command.supports(...), it would be better if we had checks against the shipped protocol version, like: if (WebInspector.backendVersion.builtBefore(WebInspector.BackendVersions.iOS9)) if (WebInspector.backendVersion.equalTo(WebInspector.BackendVersions.iOS8)) if (WebInspector.backendVersion.builtAfter(WebInspector.BackendVersions.iOS6)) Feel free to suggest better comparison operator names, these are clunky. I believe WebKit uses "builtOnOrAfter(10, 10, 0)" or similar. In the legacy protocol versions, we can embed a top-level "version" field and parse it in the frontend. And, going forward, we can use a version string of iOS9+ once a legacy copy of iOS9 has been copied over. We could also implement fine-grained feature checking, like WebInspector.backendVersion.supports("Debugger.BreakpointIgnoreCounts"), which will return false for old versions; once that specific feature support lands in trunk, we add the feature key "Debugger.BreakpointIgnoreCounts" in a file somewhere that feeds into backendVersion.supports(). Once the next legacy protocol version is created, we delete all the old feature key checks and replace them with backendVersion.equalOrLaterThan(new-version).
<rdar://problem/22519698>
iOS 9 was added to the Legacy folder last week.
I think we could just give the Inspector domain a version number. And bump it whenever we want/need to. { "domain": "Inspector", "constants": [ { "name": "Version", "value": 1000 } ] } Would generate: InspectorBackend.registerConstant("Inspector.Version", 1000); We could retroactively add it to Legacy Inspector-iOS-*.json files. And add WebInspector.BackendVersions.iOS7-9 constants (700, 800, 900) to the frontend. That said, I still think we should be feature checking the protocol when possible. This would only be used for when we can't easily do that (like new properties in types).