pwa.pwa cache runtime api risk

pwa.pwa-cache-runtime-api-risk

Rule ID: pwa.pwa-cache-runtime-api-risk Severity: ERROR Category: pwa Target Standards: W3C Service Workers (ServiceWorkerGlobalScope Execution Context), HTML Living Standard (Dedicated Worker & Web Worker Isolation), W3C Web Storage Specification (Thread Affinity Limitations)

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1. Overview & Core Invariant

Prevents access to main-thread DOM and synchronous Web Storage APIs (window, document, localStorage) inside Service Worker scripts

Core Invariant:

"Service Worker scripts must not access main-thread DOM or synchronous storage APIs (window, document, localStorage, sessionStorage, alert, confirm, prompt)."

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2. Technical Grounding & Engine Realities

Service Workers run in a distinct background worker thread (ServiceWorkerGlobalScope) that is entirely decoupled from the browser UI thread.

Attempting to access DOM APIs (window, document) or synchronous storage (localStorage, sessionStorage) in a Service Worker throws an immediate fatal ReferenceError at runtime, aborting worker installation and breaking all offline caching capabilities.

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3. Vulnerability & Risk Taxonomy

Risk Vector	Severity	Impact
Immediate Service Worker Installation Crash	HIGH	Worker script fails during parsing/evaluation with Uncaught ReferenceError: window is not defined, completely disabling offline caching.
Broken Background Push/Sync Functionality	HIGH	Background sync and push notifications fail to initialize because the worker thread crashed upon bootstrap.

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4. Non-Compliant Code Patterns (Bad Examples)

TSX (Service Worker script attempting to access window and localStorage):

<script>
  self.addEventListener("install", (event) => {
    const token = localStorage.getItem("token");
    window.location.reload();
  });
</script>

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5. Compliant Implementation Patterns (Good Examples)

TSX (Compliant Service Worker using Cache Storage and Worker primitives):

<script>
  self.addEventListener("install", (event) => {
    event.waitUntil(
      caches.open("v1").then((cache) => cache.addAll(["/", "/offline.html"]))
    );
  });
</script>

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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: pwa.pwa-cache-runtime-api-risk"]

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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 pwa.pwa-cache-runtime-api-risk 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/pwa.pwa-cache-runtime-api-risk/:

flowchart TD
    subgraph GoldenCorpus ["1-SSOT Tri-Corpus Test Matrix for pwa.pwa-cache-runtime-api-risk"]
        subgraph P ["Positive Corpus (tests/correctness/pwa.pwa-cache-runtime-api-risk/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/pwa.pwa-cache-runtime-api-risk/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/pwa.pwa-cache-runtime-api-risk/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 pwa.pwa-cache-runtime-api-risk intentional exception -->

// charites:ignore pwa.pwa-cache-runtime-api-risk intentional exception

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9. Configuration Reference (charites.yaml)

rules:
  pwa.pwa-cache-runtime-api-risk:
    severity: error # error | warn | info | off