responsive.fixed width overflow

responsive.fixed-width-overflow

Rule ID: responsive.fixed-width-overflow Severity: ERROR Category: responsive Target Standards: W3C CSS Box Sizing & Fluid Layout Standards, Mobile-First Responsive Layout Dimensions (320px Minimum Screen Width), Tailwind CSS Arbitrary Values & Constrained Width Geometry

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1. Overview & Core Invariant

Detects static fixed container widths exceeding 320px that cause horizontal overflow on mobile viewports

Core Invariant:

"Static widths and min-widths exceeding 320px on mobile baseline must be bounded by fluid constraints (max-w-full) or scoped to desktop breakpoints."

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2. Technical Grounding & Engine Realities

Compact and foldable smartphones feature viewport widths starting at 320px (e.g. early iPhone SE or folded Galaxy Z Fold).

Declaring rigid static widths greater than 320px (such as w-[500px] or min-w-[400px]) directly on the mobile baseline mechanically exceeds the physical screen boundaries, causing the page to tear and creating an unwanted horizontal scrollbar.

Using fluid widths with maximum caps (w-full max-w-lg) ensures full responsiveness across all screen dimensions.

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3. Vulnerability & Risk Taxonomy

Risk Vector	Severity	Impact
Mobile Horizontal Layout Tear	HIGH	Container forces document width beyond screen borders, creating horizontal scrolling and broken edge-swipe gestures.
Cutoff Touch Targets	MEDIUM	Buttons on the right edge of the fixed container become inaccessible without panning horizontally.

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4. Non-Compliant Code Patterns (Bad Examples)

TSX (Static fixed width exceeding 320px without fluid boundary):

<div className="w-[500px] bg-card p-4">
  <p>Kartu Informasi Desa</p>
</div>

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5. Compliant Implementation Patterns (Good Examples)

TSX (Fluid mobile width with max-width ceiling on larger screens):

<div className="w-full max-w-lg bg-card p-4">
  <p>Kartu Informasi Desa</p>
</div>

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

This rule evaluates source code through the standard AST inspection pipeline:

flowchart TD
    Node["AST Node (Astro / TSX element)"] --> Inspect["1. Inspect Element & Attributes"]
    Inspect --> Invariant{"2. Evaluate Rule Invariant"}
    Invariant -- "Compliant" --> Safe["Pass"]
    Invariant -- "Non-Compliant" --> IgnoreCheck{"3. Check charites:ignore directive"}
    IgnoreCheck -- "Ignored" --> Safe
    IgnoreCheck -- "Not Ignored" --> Diag["4. Emit Diagnostic: responsive.fixed-width-overflow"]

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Step-by-Step Evaluation:

1. AST Traversal: Visits normalized ir.Node structures during AST streaming.
2. Invariant Check: Compares node attributes against rule invariants.
3. Directive Suppression Check: Honors inline charites:ignore responsive.fixed-width-overflow directives.
4. Diagnostic Emission: Emits compiler-grade diagnostic on invariant violation.

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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/responsive.fixed-width-overflow/:

flowchart TD
    subgraph GoldenCorpus ["1-SSOT Tri-Corpus Test Matrix for responsive.fixed-width-overflow"]
        subgraph P ["Positive Corpus (tests/correctness/responsive.fixed-width-overflow/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/responsive.fixed-width-overflow/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/responsive.fixed-width-overflow/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 responsive.fixed-width-overflow intentional exception -->

// charites:ignore responsive.fixed-width-overflow intentional exception

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9. Configuration Reference (charites.yaml)

rules:
  responsive.fixed-width-overflow:
    severity: error # error | warn | info | off