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Parse Failure Rate

Measuring code health through parsing success

What is Parse Failure Rate?

Parse failure rate measures the percentage of files in your repository that couldn't be successfully parsed by Spec This's code analysis engine. A file fails to parse when it contains syntax errors, uses unsupported language features, or is corrupted.

This metric is important because unparseable files prevent accurate code analysis and often indicate underlying problems with code quality, build processes, or development practices.

How It's Calculated

Formula

Parse Failure Rate = (Files Failed / Total Files) × 100%

Example 1:

  • Total files scanned: 500
  • Files that failed: 5
  • Parse failure rate: (5 / 500) × 100% = 1%

Example 2:

  • Total files scanned: 200
  • Files that failed: 15
  • Parse failure rate: (15 / 200) × 100% = 7.5%

Common Causes of Parse Failures

1. Syntax Errors

The most common cause - code that doesn't follow JavaScript/TypeScript syntax rules.

// Missing closing brace
function calculate(x, y) {
  return x + y;
// ❌ Parse error: missing }

// Invalid syntax
const value = ;  // ❌ Parse error: unexpected token

// Mismatched brackets
const arr = [1, 2, 3};  // ❌ Parse error: expected ]

// Invalid JSX
const Component = () => {
  return <div>Hello  // ❌ Parse error: unclosed tag
};

2. Incomplete or Work-in-Progress Files

Files that are mid-refactoring or not yet complete.

// WIP file with placeholder code
export function processData() {
  // TODO: implement this
  const result =   // ❌ Incomplete statement

  return
}

// Commented-out code with invalid syntax
// function old_code( {
//   return "test"
// ❌ Parser attempts to read this

3. Experimental or Cutting-Edge Syntax

Using JavaScript/TypeScript features not yet supported by the parser.

// Stage 1 proposal syntax not widely supported
const obj = {
  property = initialValue  // ❌ Might not parse
};

// Experimental decorators with non-standard syntax
@customDecorator({ options })
class MyClass { }  // ❌ Depending on parser version

4. Build Artifacts or Generated Code

Malformed generated files or corrupted build outputs.

Examples:

  • Partially written compiled output
  • Corrupted minified files
  • Incomplete code generation
  • Merge conflict markers left in code

5. Wrong File Type Scanned

Files with .js/.ts extensions that aren't actually JavaScript/TypeScript.

Examples:

  • JSON files misnamed with .js extension
  • Template files that need preprocessing
  • Data files accidentally included

Why Parse Failures Matter

Analysis Impact

  • Prevents accurate complexity metrics
  • Hides dependencies and relationships
  • Skips security analysis
  • Incomplete code intelligence
  • Missing in dependency graphs

Development Impact

  • May indicate broken code
  • Suggests poor build processes
  • Could break production
  • Incomplete refactorings
  • Neglected technical debt

Recommended Thresholds

Sensitivity LevelMax RateInterpretation
High≤ 1%Well-maintained, production-ready code
Medium≤ 5%Active development, some WIP acceptable
Low≤ 10%Heavy refactoring or migration in progress

⚠️ Above 10%

A parse failure rate above 10% is a red flag indicating serious code health issues. This should be investigated and resolved immediately, as it likely indicates:

  • Broken build processes
  • Corrupted repository state
  • Extensive uncommitted work
  • Incorrect file inclusion in scans

How to Investigate Parse Failures

1. Review the Scan Report

Spec This provides detailed information about which files failed and why. Check the scan results in the Scans page to see:

  • File paths that failed
  • Error messages and line numbers
  • Type of parse error

2. Check Your Linter

Run your linter (ESLint, TSLint) to catch syntax errors:

# Check specific file
npx eslint src/problematic-file.ts

# Check all files
npx eslint src/**/*.ts

3. Verify TypeScript Compilation

If using TypeScript, ensure files compile:

# Type check without emitting files
npx tsc --noEmit

# Check specific file
npx tsc --noEmit src/problematic-file.ts

4. Search for Common Issues

Look for these common problems in failed files:

  • Merge conflict markers (<<<<<<<, =======, >>>>>>>)
  • Mismatched brackets or braces
  • Unclosed strings or template literals
  • Invalid JSX syntax

5. Update .gitignore

If build artifacts or generated files are being scanned, exclude them:

# .gitignore
dist/
build/
*.generated.js
.next/
coverage/

Preventing Parse Failures

Best Practices

  • Use a linter: Configure ESLint or TSLint to catch syntax errors before commit
  • Enable pre-commit hooks: Use tools like Husky to run linters automatically
  • CI/CD checks: Fail builds if linting fails
  • Keep build artifacts out: Properly configure .gitignore
  • Complete refactorings: Don't commit half-finished code to main branches
  • Review scan reports: Regularly check parse failure reports and address issues
  • Standardize tooling: Ensure all developers use compatible parser versions

Related Considerations

  • Build Success Rate: Parse failures often correlate with build failures
  • Test Coverage: Unparseable files can't be included in coverage reports
  • Code Quality Trends: Increasing parse failures indicate declining code health