theme.focus ring hardcode

theme.focus-ring-hardcode

Rule ID: theme.focus-ring-hardcode Severity: WARN Category: theme Target Standards: WCAG 2.2 Success Criterion 2.4.11 (Focus Not Obscured), WCAG 2.2 Success Criterion 2.4.13 (Focus Appearance), W3C DTCG State & Focus Tokens

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1. Overview & Core Invariant

Detects hardcoded primitive palette or arbitrary hex colors on focus rings and outlines

Core Invariant:

"Keyboard focus indicator colors must be driven by semantic ring design tokens (e.g. ring-ring), never primitive palette or hardcoded hex colors."

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2. Technical Grounding & Engine Realities

Specifying raw hex literals or primitive colors on focus rings (e.g. focus:ring-[#3b82f6] or ring-blue-500) creates severe accessibility and theme regressions:

1. WCAG Contrast Failures: Static blue or hex rings fail the minimum 3:1 contrast ratio against dark or tinted component backgrounds.
2. Theme Blindness: A ring-offset-white class flashes a glaring white halo when tabbed in dark mode.
3. Fragmented Keyboard Affordance: Keyboard navigation users experience jarringly different focus indicators across distinct views.

Charites enforces using semantic focus tokens (e.g. focus-visible:ring-ring or ring-ring) and token-driven offsets (ring-offset-background).

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3. Vulnerability & Risk Taxonomy

Risk Vector	Severity	Impact
WCAG 2.4.13 Non-Compliance	HIGH	Low-vision and keyboard users cannot perceive the active focus indicator due to inadequate contrast ratios.
Dark Mode Halo Inversion	MEDIUM	Hardcoded light offsets create blinding light borders around active inputs on dark surfaces.

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4. Non-Compliant Code Patterns (Bad Examples)

TSX (Arbitrary hex and primitive focus ring in JSX):

<button className="focus:ring-[#3b82f6] focus:ring-2">Sign in</button>

ASTRO (Primitive ring and static offset in Astro):

<input class="ring-blue-500 ring-offset-white focus:outline-blue-500" />

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5. Compliant Implementation Patterns (Good Examples)

TSX (Using semantic focus ring token):

<button className="focus-visible:ring-2 focus-visible:ring-ring focus-visible:ring-offset-2">Sign in</button>

ASTRO (Semantic ring and background-adaptive offset):

<input class="focus:ring-2 focus:ring-ring ring-offset-background" />

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6. Detection & Verification Pipeline (How The Rule Evaluates Code)

This theme rule evaluates source templates against the project's design token graph:

flowchart TD
    Node["AST Node (Astro / TSX element)"] --> Extract["1. Extract Class Names (e.g. 'hover:bg-primary/10')"]
    Extract --> Strip["2. Strip Variants (hover:, dark:, sm:) -> 'bg-primary/10'"]
    Strip --> Split["3. Split Opacity Modifier -> Utility: 'bg-primary', Opacity: '/10'"]
    Split --> Convention["4. Query TokenConvention (Candidate: '--color-primary-light')"]
    Convention --> GraphQuery{"5. Check Token Graph (Does token exist in active scope?)"}
    GraphQuery -- "No (Banana Test)" --> Safe["Pass (Valid Custom / Untokenized Color)"]
    GraphQuery -- "Yes (Official Token Exists)" --> IgnoreCheck{"6. Check charites:ignore directive"}
    IgnoreCheck -- "Ignored" --> Safe
    IgnoreCheck -- "Not Ignored" --> Diag["7. Emit Diagnostic: theme.focus-ring-hardcode with Replacement Suggestion"]

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Step-by-Step Evaluation:

1. AST Node Traversal: internal/analyzer streams JSX/Astro AST elements to the rule's Evaluate visitor.
2. Variant Normalization: Strips responsive (sm:, md:), interaction state (hover:, focus:), and theme (dark:) prefixes to isolate the core utility class.
3. Modifier Extraction: Parses utility segments and extracts slash opacity modifiers.
4. Token Convention Resolution: Consults the TokenConvention adapter to determine the official semantic design token replacement candidate.
5. Token Graph Verification (Banana Test): Queries token.Context to verify that the candidate token is declared in global.css or tokens.json within the element's scope. If not declared, the custom value is permitted without a false-positive diagnostic.
6. Directive Suppression Check: Inspects preceding AST comments for charites:ignore theme.focus-ring-hardcode.
7. Diagnostic Emission: Produces a structured diagnostic with line number, column span, and actionable replacement suggestion.

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7. Verification & Test Harness (How The Test Works: 1-SSOT Tri-Corpus)

This rule is rigorously tested and validated across the canonical 1-SSOT Tri-Corpus in tests/correctness/theme.focus-ring-hardcode/:

flowchart TD
    subgraph GoldenCorpus ["1-SSOT Tri-Corpus Test Matrix for theme.focus-ring-hardcode"]
        subgraph P ["Positive Corpus (tests/correctness/theme.focus-ring-hardcode/positive/)"]
            P1["P1: Obvious Direct Violation"]
            P2["P2: Indirect / Variant Concatenation"]
            P3["P3: Helper / clsx / cn Wrapper"]
            P4["P4: Deeply Nested Elements"]
            P5["P5: Aliased Imports / Re-exports"]
        end
        subgraph N ["Negative Corpus (tests/correctness/theme.focus-ring-hardcode/negative/)"]
            N1["N1: Valid Design Tokens"]
            N2["N2: Explicit charites:ignore Directive"]
            N3["N3: Third-Party / Vendor Components"]
            N4["N4: Clean Semantic HTML"]
            N5["N5: Untokenized Custom Values (Banana Test)"]
        end
        subgraph A ["Adversarial Corpus (tests/correctness/theme.focus-ring-hardcode/adversarial/)"]
            A1["A1: Template Literal Interpolations"]
            A2["A2: Ternary Conditional Expressions"]
            A3["A3: Spread Properties & Dynamic Overrides"]
            A4["A4: Dynamic Object Class Syntax"]
            A5["A5: Shadowed Variable Identifiers"]
            A6["A6: Nested Closures & HOC Wrappers"]
            A7["A7: Obfuscated Classes & Cyclic Tokens"]
        end
    end

    P --> TestRunner["Automated Runner (rule_test.go)"]
    N --> TestRunner
    A --> TestRunner
    TestRunner --> Gates["Quality Gates: Zero Panic, Zero False-Positive, Zero Bypass"]

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• Positive Fixtures (P1-P5): Verified to trigger diagnostics at exact lines and column spans.
• Negative Fixtures (N1-N5): Verified to produce zero diagnostics on valid tokens and legitimate exemptions.
• Adversarial Fixtures (A1-A7): Verified to prevent evasion across dynamic expressions, string interpolations, and cyclic references.

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8. How to Suppress (Ignore Directives)

If this pattern is required for an intentional exception, suppress the diagnostic using the canonical Charites Rule ID:

<!-- charites:ignore theme.focus-ring-hardcode intentional exception -->

// charites:ignore theme.focus-ring-hardcode intentional exception

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9. Configuration Reference (charites.yaml)

rules:
  theme.focus-ring-hardcode:
    severity: warn # error | warn | info | off