[Experimental] Opt-in @Environment resolution to prevent warnings during inspection

[garry-jeromson]

Problem

When ViewInspector evaluates a custom view's body, any @Environment properties still in their .keyPath state trigger:

Accessing Environment<T>'s value outside of being installed on a View. This will always read the default value and will not update.

In large test suites this can produce thousands of warnings (e.g. ~4,000 in ours), making it difficult to spot real issues in test output.

Related issues: #131, #167, #338

Solution

This PR adds opt-in @Environment resolution that transitions fields from .keyPath to .value state before body evaluation, eliminating the warnings entirely.

Enabling

// Per-test
override func setUp() {
    ViewInspectorConfig.resolveEnvironmentValues = true
}

// Or via environment variable (e.g. in your test scheme/CI)
VIEWINSPECTOR_RESOLVE_ENVIRONMENT=1

Custom environment values

Test code using .environment() modifiers is automatically honored during resolution — both standard SwiftUI keys and custom EnvironmentKey types:

// Standard key override
let sut = MyView().environment(\.colorScheme, .dark)
let text = try sut.inspect().find(ViewType.Text.self).string()
XCTAssertEqual(text, "dark") // ✅ Uses the override, not the default

// Custom EnvironmentKey
let sut = MyView().environment(\.myCustomKey, "custom_value")
let text = try sut.inspect().find(ViewType.Text.self).string()
XCTAssertEqual(text, "custom_value") // ✅ Custom keys work too

Technical approach

• EnvironmentResolvable protocol — conformance on Environment<Value> enables type-erased generic resolution via _resolve(using:)
• AnyWritableEnvironmentKeyPath protocol — conformance on WritableKeyPath<EnvironmentValues, T> enables type-erased application of .environment() modifier overrides
• Raw byte manipulation of @frozen @Environment<Value> enum layout (.keyPath → .value state transition)
• Keypath-pointer-only matching — when sizeof(Value) > sizeof(KeyPath), Mirror-extracted copies have divergent spare payload bytes; matching only the keypath pointer (which is unique per field) avoids false negatives
• ARC safety — action/closure-based environment values are skipped; buildValueStateBytes uses raw memory allocation to avoid corrupting reference-counted keypath fields
• Thread safety — environment values flow through the call chain as parameters, no mutable static state

⚠️ Experimental — caveats

This is an experimental approach that relies on @Environment's @frozen ABI-stable layout. It works reliably in our test suite but should be considered carefully before broader adoption:

1. @frozen dependency — the implementation assumes @Environment<Value> uses a two-case enum (keyPath/value) with a specific byte layout. This is ABI-stable but not a public API contract.

2. Value types only — resolution is skipped for @Environment values that contain reference types (closures, classes). Action-type environments like \.dismiss and \.openURL are safely ignored.

3. Resolved values are defaults unless overridden — without .environment() modifiers, values come from EnvironmentValues() (SwiftUI defaults). Custom keys use their EnvironmentKey.defaultValue.

Files changed

File	Description
EnvironmentInjection.swift	Core resolution logic, ViewInspectorConfig, EnvironmentResolvable, AnyWritableEnvironmentKeyPath
ContentExtraction.swift	Hook points: resolve before copy.body / copy.body(), thread environmentModifiers parameter
CustomView.swift	Pass medium.environmentModifiers through to extractContent
EnvironmentInjectionTests.swift	16 test cases covering protocol, resolution, integration, custom keys, and regression

Test coverage

• ✅ Bool, enum, action environment types
• ✅ Resolution enabled/disabled (opt-in flag)
• ✅ Single and multiple @Environment fields
• ✅ Mixed @Environment + @EnvironmentObject
• ✅ ViewModifier with @Environment
• ✅ Standard key override via .environment() modifier
• ✅ Custom EnvironmentKey override via .environment() modifier
• ✅ Default values when no override present
• ✅ Existing @EnvironmentObject injection unaffected
• ✅ All 1,480 existing ViewInspector tests pass

[nalexn]

This is very interesting, thanks for the PR! I hope I'll get some free time soon to explore this more and merge.