jsdoc-type-pratt-parser/src/parslets/FunctionParslet.ts

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import { composeParslet, type ParsletFunction } from './Parslet.js'
import { Precedence } from '../Precedence.js'
import type { FunctionResult, RootResult } from '../result/RootResult.js'
import type { IntermediateResult } from '../result/IntermediateResult.js'
import type { KeyValueResult, NonRootResult } from '../result/NonRootResult.js'
import { UnexpectedTypeError } from '../errors.js'
import { assertPlainKeyValueOrRootResult } from '../assertTypes.js'

export function getParameters (value: IntermediateResult): Array<RootResult | KeyValueResult> {
  let parameters: NonRootResult[] = []
  if (value.type === 'JsdocTypeParameterList') {
    parameters = value.elements
  } else if (value.type === 'JsdocTypeParenthesis') {
    parameters = [value.element]
  } else {
    throw new UnexpectedTypeError(value)
  }

  return parameters.map(p => assertPlainKeyValueOrRootResult(p))
}

export function getUnnamedParameters (value: IntermediateResult): RootResult[] {
  const parameters = getParameters(value)
  if (parameters.some(p => p.type === 'JsdocTypeKeyValue')) {
    throw new Error('No parameter should be named')
  }
  return parameters as RootResult[]
}

export function createFunctionParslet ({ allowNamedParameters, allowNoReturnType, allowWithoutParenthesis, allowNewAsFunctionKeyword }: {
  allowNamedParameters?: string[]
  allowWithoutParenthesis: boolean
  allowNoReturnType: boolean
  allowNewAsFunctionKeyword: boolean
}): ParsletFunction {
  return composeParslet({
    name: 'functionParslet',
    accept: (type, next) => type === 'function' || (allowNewAsFunctionKeyword && type === 'new' && next === '('),
    parsePrefix: parser => {
      const newKeyword = parser.consume('new')
      parser.consume('function')

      const hasParenthesis = parser.lexer.current.type === '('

      if (!hasParenthesis) {
        if (!allowWithoutParenthesis) {
          throw new Error('function is missing parameter list')
        }

        return {
          type: 'JsdocTypeName',
          value: 'function'
        }
      }

      let result: FunctionResult = {
        type: 'JsdocTypeFunction',
        parameters: [],
        arrow: false,
        constructor: newKeyword,
        parenthesis: hasParenthesis
      }

      const value = parser.parseIntermediateType(Precedence.FUNCTION)

      if (allowNamedParameters === undefined) {
        result.parameters = getUnnamedParameters(value)
      } else if (newKeyword && value.type === 'JsdocTypeFunction' && value.arrow) {
        result = value
        result.constructor = true
        return result
      } else {
        result.parameters = getParameters(value)
        for (const p of result.parameters) {
          if (p.type === 'JsdocTypeKeyValue' && (!allowNamedParameters.includes(p.key))) {
            throw new Error(`only allowed named parameters are ${allowNamedParameters.join(', ')} but got ${p.type}`)
          }
        }
      }

      if (parser.consume(':')) {
        result.returnType = parser.parseType(Precedence.PREFIX)
      } else {
        if (!allowNoReturnType) {
          throw new Error('function is missing return type')
        }
      }

      return result
    }
  })
}