apisurf/lib/utilities/parseInterfaceDefinition.js

Analyze API surface changes between npm package versions to catch breaking changes

/**
 * Parse interface definition from source lines
 */
export function parseInterfaceDefinition(lines, startIndex, name) {
    const properties = [];
    let braceCount = 0;
    let inInterface = false;
    for (let i = startIndex; i < lines.length; i++) {
        const line = lines[i].trim();
        // Count the brace level before parsing
        const prevBraceCount = braceCount;
        // Count braces
        const openBraces = (line.match(/{/g) || []).length;
        const closeBraces = (line.match(/}/g) || []).length;
        if (openBraces > 0) {
            braceCount += openBraces;
            if (!inInterface) {
                inInterface = true;
            }
        }
        // Only parse properties at the top level (braceCount === 1 BEFORE counting this line's braces)
        if (inInterface && prevBraceCount === 1 && !line.startsWith('}')) {
            // Match properties like: propertyName: type; or propertyName?: type;
            // This includes properties with object types like: user: { ... }
            const propMatch = line.match(/^\s*(\w+)(\?)?:\s*/);
            if (propMatch && !line.match(/^\s*\w+\s*\(/)) { // Not a method
                properties.push({
                    name: propMatch[1],
                    required: !propMatch[2]
                });
            }
            // Match method signatures like: methodName(): void;
            else if (line.match(/^\s*(\w+)(\?)?\s*\(/)) {
                const methodMatch = line.match(/^\s*(\w+)(\?)?\s*\(/);
                if (methodMatch) {
                    properties.push({
                        name: methodMatch[1],
                        required: !methodMatch[2]
                    });
                }
            }
        }
        if (closeBraces > 0) {
            braceCount -= closeBraces;
            if (braceCount === 0) {
                break;
            }
        }
    }
    return {
        name,
        kind: 'interface',
        extendedProperties: properties,
        signature: `export interface ${name} { ${properties.map(p => `${p.name}${p.required ? '' : '?'}: any`).join('; ')} }`
    };
}