browser.safari only api

browser.safari-only-api

Rule ID: browser.safari-only-api Severity: WARN Category: browser Target Standards: W3C Web App Manifest (display-mode: standalone), W3C Pointer Events Level 3, Apple Pay on the Web Guidelines (Feature Detection Requirements)

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1. Overview & Core Invariant

Flags unguarded Apple WebKit/Safari-proprietary APIs without universal web platform fallbacks

Core Invariant:

"Direct invocation of Apple Safari-exclusive APIs ('navigator.standalone', 'ApplePaySession', iOS gesture events) must provide W3C standard fallbacks for Android and desktop platforms."

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2. Technical Grounding & Engine Realities

Apple WebKit includes proprietary features designed exclusively for iOS/macOS Safari.

Calling 'navigator.standalone' directly will always return undefined on Android Chrome, while calling 'ApplePaySession.canMakePayments()' without checking 'window.ApplePaySession' throws ReferenceError crashes.

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3. Vulnerability & Risk Taxonomy

Risk Vector	Severity	Impact
Crash on Non-Apple Platforms	MEDIUM	Calling 'ApplePaySession.canMakePayments()' on Android Chrome, Windows Edge, or Linux Firefox throws 'ReferenceError: ApplePaySession is not defined'.
Broken PWA Detection on Android	MEDIUM	Using 'navigator.standalone' fails to detect installed PWAs on Android, where 'display-mode: standalone' is the universal standard.

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4. Non-Compliant Code Patterns (Bad Examples)

JAVASCRIPT (Direct invocation of ApplePaySession without availability check):

if (ApplePaySession.canMakePayments()) {
  showApplePayButton();
}

JAVASCRIPT (Relying solely on iOS-proprietary navigator.standalone):

const isAppMode = navigator.standalone;

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5. Compliant Implementation Patterns (Good Examples)

JAVASCRIPT (Defensive feature guard before ApplePaySession invocation):

if (typeof window !== "undefined" && window.ApplePaySession && window.ApplePaySession.canMakePayments()) {
  showApplePayButton();
}

JAVASCRIPT (Standard W3C display-mode with legacy iOS fallback):

const isAppMode = (typeof window !== "undefined" && window.matchMedia("(display-mode: standalone)").matches) ||
  (typeof navigator !== "undefined" && Boolean(navigator.standalone));

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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: browser.safari-only-api"]

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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 browser.safari-only-api 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/browser.safari-only-api/:

flowchart TD
    subgraph GoldenCorpus ["1-SSOT Tri-Corpus Test Matrix for browser.safari-only-api"]
        subgraph P ["Positive Corpus (tests/correctness/browser.safari-only-api/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/browser.safari-only-api/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/browser.safari-only-api/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 browser.safari-only-api intentional exception -->

// charites:ignore browser.safari-only-api intentional exception

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9. Configuration Reference (charites.yaml)

rules:
  browser.safari-only-api:
    severity: warn # error | warn | info | off