Errors.md

Errors

This module provides custom error classes for handling parsing failures and AST-related errors.

ParseError

The ParseError class is thrown when the parser encounters invalid CSS syntax or fails to parse the input string.

Properties

name

Type: String
Value: 'ParseError'

message

Type: String

The error message describing what went wrong during parsing.

stack

Type: String

The error stack trace from the underlying parsing error.

Example Usage

const { parse } = require('postcss-values-parser');

try {
  const root = parse('invalid css syntax @#$%');
} catch (error) {
  if (error instanceof ParseError) {
    console.log(error.name); // 'ParseError'
    console.log(error.message); // Description of the parsing error
  }
}

AstError

The AstError class is thrown when the AST (Abstract Syntax Tree) is invalid or empty after parsing.

Properties

name

Type: String
Value: 'AstError'

message

Type: String
Value: 'Invalid or empty AST'

Example Usage

const { parse } = require('postcss-values-parser');

try {
  const root = parse('');
} catch (error) {
  if (error instanceof AstError) {
    console.log(error.name); // 'AstError'
    console.log(error.message); // 'Invalid or empty AST'
  }
}

Error Handling Best Practices

When using postcss-values-parser, it's recommended to handle both error types:

const { parse, ParseError, AstError } = require('postcss-values-parser');

function safeParseValue(css) {
  try {
    return parse(css);
  } catch (error) {
    if (error instanceof ParseError) {
      console.error('Failed to parse CSS value:', error.message);
      // Handle parsing syntax errors
    } else if (error instanceof AstError) {
      console.error('Invalid AST generated:', error.message);
      // Handle empty or invalid AST
    } else {
      console.error('Unexpected error:', error);
      // Handle other unexpected errors
    }
    return null;
  }
}

Notes

• Both error classes extend the standard JavaScript Error class
• ParseError wraps errors from the underlying CSS parser
• AstError indicates issues with the generated AST structure
• Error messages provide context about what went wrong during parsing
• Stack traces are preserved for debugging purposes