theme.dynamic class

theme.dynamic-class

Rule ID: theme.dynamic-class Severity: ERROR Category: theme Target Standards: Tailwind CSS JIT Static Analysis & Extraction Guidelines, Build-Time CSS Zero-Runtime Architecture, W3C Web Performance & Production Reliability

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1. Overview & Core Invariant

Detects unpadded dynamic template strings breaking Tailwind JIT class generation

Core Invariant:

"Utility classes must be written as complete static string literals so the Tailwind build compiler can reliably extract and generate them."

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2. Technical Grounding & Engine Realities

Tailwind CSS searches source files using regular expressions looking for complete class strings at build time. It does not evaluate JavaScript at runtime.

When developers dynamically construct utility classes using template literal slicing (e.g. className={text-${color}-500} or bg-${variant}):

1. Missing Production CSS: The Tailwind compiler never matches the interpolated string, leaving the utility completely absent from the production stylesheet.
2. Silent Visual Degradation: The component appears broken or unstyled in production while appearing to work intermittently in dev if another component imported that class.
3. Inscrutable Debugging: Developers struggle to trace why specific color variants intermittently fail to render.

Charites enforces using static class maps or complete utility strings within conditional expressions.

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3. Vulnerability & Risk Taxonomy

Risk Vector	Severity	Impact
Missing Production Styles	CRITICAL	Tailwind JIT engine strips un-scanned utility classes from production bundles, breaking layout and colors.
Heisenbug UI Regressions	HIGH	Styles intermittently vanish or break depending on which other files are compiled in the same build chunk.

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4. Non-Compliant Code Patterns (Bad Examples)

TSX (Dynamic class string splicing in JSX className):

<div className={`text-${color}-500 font-bold`}>Status</div>

ASTRO (Dynamic background variant splicing in Astro):

<button class={`px-4 py-2 bg-${variant}`}>Action</button>

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5. Compliant Implementation Patterns (Good Examples)

TSX (Static class lookup map for dynamic variants):

const colorMap: Record<string, string> = {
  red: "text-red-500",
  blue: "text-blue-500",
  green: "text-green-500",
};
<div className={`${colorMap[color]} font-bold`}>Status</div>

TSX (Complete utility class strings in ternary expression):

<button className={`px-4 py-2 ${isActive ? "bg-primary text-primary-foreground" : "bg-muted"}`}>Action</button>

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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.dynamic-class 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.dynamic-class.
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.dynamic-class/:

flowchart TD
    subgraph GoldenCorpus ["1-SSOT Tri-Corpus Test Matrix for theme.dynamic-class"]
        subgraph P ["Positive Corpus (tests/correctness/theme.dynamic-class/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.dynamic-class/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.dynamic-class/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.dynamic-class intentional exception -->

// charites:ignore theme.dynamic-class intentional exception

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9. Configuration Reference (charites.yaml)

rules:
  theme.dynamic-class:
    severity: error # error | warn | info | off