theme.unlayered token definition

theme.unlayered-token-definition

Rule ID: theme.unlayered-token-definition Severity: ERROR Category: theme Target Standards: W3C Cascading Style Sheets (CSS) Level 5 (Cascade Layers), W3C CSS Custom Properties for Cascading Variables Module Level 1

---

1. Overview & Core Invariant

Detects CSS custom property definitions declared outside @layer theme or @layer base

Core Invariant:

"CSS custom properties representing theme tokens must be declared within @layer theme or @layer base to ensure deterministic cascade resolution."

---

2. Technical Grounding & Engine Realities

In modern frontend architectures and Tailwind CSS v4, unlayered CSS custom properties automatically take precedence over all layered styles regardless of specificity.

When developers declare :root { --primary: #... } without @layer theme or @layer base:

1. Cascade Inversion: Unlayered rules override framework layers and variant cascades unexpectedly.
2. Dark Mode Clashes: Nested dark mode themes defined within layers cannot reliably override unlayered root variables.
3. Specificity Pollution: Subsequent theme overrides require !important or higher specificity hacks to function.

Charites enforces encapsulating theme custom property definitions inside @layer theme or @layer base.

---

3. Vulnerability & Risk Taxonomy

Risk Vector	Severity	Impact
Cascade Priority Inversion	HIGH	Unlayered properties override all cascade layers, preventing dark mode and variant styles from taking effect.
Theme Specificity Escalation	MEDIUM	Teams resort to !important declarations to override unlayered variables, causing style degradation.

---

4. Non-Compliant Code Patterns (Bad Examples)

ASTRO (Unlayered :root custom property definition in style tag):

<style>
  :root {
    --primary: #2563eb;
    --background: #ffffff;
  }
</style>

TSX (Unlayered [data-theme] custom property definition):

export function GlobalStyles() {
  return (
    <style>{`
      :root {
        --brand-color: #3b82f6;
      }
    `}</style>
  );
}

---

5. Compliant Implementation Patterns (Good Examples)

ASTRO (Enclosed within @layer theme):

<style>
  @layer theme {
    :root {
      --primary: #2563eb;
      --background: #ffffff;
    }
  }
</style>

ASTRO (Enclosed within @layer base):

<style>
  @layer base {
    :root {
      --primary: #2563eb;
    }
  }
</style>

---

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.unlayered-token-definition with Replacement Suggestion"]

Loading

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.unlayered-token-definition.
7. Diagnostic Emission: Produces a structured diagnostic with line number, column span, and actionable replacement suggestion.

---

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.unlayered-token-definition/:

flowchart TD
    subgraph GoldenCorpus ["1-SSOT Tri-Corpus Test Matrix for theme.unlayered-token-definition"]
        subgraph P ["Positive Corpus (tests/correctness/theme.unlayered-token-definition/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.unlayered-token-definition/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.unlayered-token-definition/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"]

Loading

• 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.

---

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.unlayered-token-definition intentional exception -->

// charites:ignore theme.unlayered-token-definition intentional exception

---

9. Configuration Reference (charites.yaml)

rules:
  theme.unlayered-token-definition:
    severity: error # error | warn | info | off