v-on-handler-style.js

/**
 * @author Yosuke Ota <https://github.com/ota-meshi>
 * See LICENSE file in root directory for full license.
 */
'use strict'

const utils = require('../utils')

/**
 * @typedef {import('eslint').ReportDescriptorFix} ReportDescriptorFix
 * @typedef {'method' | 'inline' | 'inline-function'} HandlerKind
 * @typedef {object} ObjectOption
 * @property {boolean} [ignoreIncludesComment]
 */

/**
 * @param {RuleContext} context
 */
function parseOptions(context) {
  /** @type {[HandlerKind | HandlerKind[] | undefined, ObjectOption | undefined]} */
  const options = /** @type {any} */ (context.options)
  /** @type {HandlerKind[]} */
  const allows = []
  if (options[0]) {
    if (Array.isArray(options[0])) {
      allows.push(...options[0])
    } else {
      allows.push(options[0])
    }
  } else {
    allows.push('method', 'inline-function')
  }

  const option = options[1] || {}
  const ignoreIncludesComment = !!option.ignoreIncludesComment

  return { allows, ignoreIncludesComment }
}

/**
 * Check whether the given token is a quote.
 * @param {Token} token The token to check.
 * @returns {boolean} `true` if the token is a quote.
 */
function isQuote(token) {
  return (
    token != null &&
    token.type === 'Punctuator' &&
    (token.value === '"' || token.value === "'")
  )
}
/**
 * Check whether the given node is an identifier call expression. e.g. `foo()`
 * @param {Expression} node The node to check.
 * @returns {node is CallExpression & {callee: Identifier}}
 */
function isIdentifierCallExpression(node) {
  if (node.type !== 'CallExpression') {
    return false
  }
  if (node.optional) {
    // optional chaining
    return false
  }
  const callee = node.callee
  return callee.type === 'Identifier'
}

/**
 * Returns a call expression node if the given VOnExpression or BlockStatement consists
 * of only a single identifier call expression.
 * e.g.
 *   @click="foo()"
 *   @click="{ foo() }"
 *   @click="foo();;"
 * @param {VOnExpression | BlockStatement} node
 * @returns {CallExpression & {callee: Identifier} | null}
 */
function getIdentifierCallExpression(node) {
  /** @type {ExpressionStatement} */
  let exprStatement
  let body = node.body
  while (true) {
    const statements = body.filter((st) => st.type !== 'EmptyStatement')
    if (statements.length !== 1) {
      return null
    }
    const statement = statements[0]
    if (statement.type === 'ExpressionStatement') {
      exprStatement = statement
      break
    }
    if (statement.type === 'BlockStatement') {
      body = statement.body
      continue
    }
    return null
  }
  const expression = exprStatement.expression
  if (!isIdentifierCallExpression(expression)) {
    return null
  }
  return expression
}

module.exports = {
  meta: {
    type: 'suggestion',
    docs: {
      description: 'enforce writing style for handlers in `v-on` directives',
      categories: undefined,
      url: 'https://eslint.vuejs.org/rules/v-on-handler-style.html'
    },
    fixable: 'code',
    schema: [
      {
        oneOf: [
          { enum: ['inline', 'inline-function'] },
          {
            type: 'array',
            items: [
              { const: 'method' },
              { enum: ['inline', 'inline-function'] }
            ],
            uniqueItems: true,
            additionalItems: false,
            minItems: 2,
            maxItems: 2
          }
        ]
      },
      {
        type: 'object',
        properties: {
          ignoreIncludesComment: {
            type: 'boolean'
          }
        },
        additionalProperties: false
      }
    ],
    messages: {
      preferMethodOverInline:
        'Prefer method handler over inline handler in v-on.',
      preferMethodOverInlineWithoutIdCall:
        'Prefer method handler over inline handler in v-on. Note that you may need to create a new method.',
      preferMethodOverInlineFunction:
        'Prefer method handler over inline function in v-on.',
      preferMethodOverInlineFunctionWithoutIdCall:
        'Prefer method handler over inline function in v-on. Note that you may need to create a new method.',
      preferInlineOverMethod:
        'Prefer inline handler over method handler in v-on.',
      preferInlineOverInlineFunction:
        'Prefer inline handler over inline function in v-on.',
      preferInlineOverInlineFunctionWithMultipleParams:
        'Prefer inline handler over inline function in v-on. Note that the custom event must be changed to a single payload.',
      preferInlineFunctionOverMethod:
        'Prefer inline function over method handler in v-on.',
      preferInlineFunctionOverInline:
        'Prefer inline function over inline handler in v-on.'
    }
  },
  /** @param {RuleContext} context */
  create(context) {
    const { allows, ignoreIncludesComment } = parseOptions(context)

    /** @type {Set<VElement>} */
    const upperElements = new Set()
    /** @type {Map<string, number>} */
    const methodParamCountMap = new Map()
    /** @type {Identifier[]} */
    const $eventIdentifiers = []

    /**
     * Verify for inline handler.
     * @param {VOnExpression} node
     * @param {HandlerKind} kind
     * @returns {boolean} Returns `true` if reported.
     */
    function verifyForInlineHandler(node, kind) {
      switch (kind) {
        case 'method': {
          return verifyCanUseMethodHandlerForInlineHandler(node)
        }
        case 'inline-function': {
          reportCanUseInlineFunctionForInlineHandler(node)
          return true
        }
      }
      return false
    }
    /**
     * Report for method handler.
     * @param {Identifier} node
     * @param {HandlerKind} kind
     * @returns {boolean} Returns `true` if reported.
     */
    function reportForMethodHandler(node, kind) {
      switch (kind) {
        case 'inline':
        case 'inline-function': {
          context.report({
            node,
            messageId:
              kind === 'inline'
                ? 'preferInlineOverMethod'
                : 'preferInlineFunctionOverMethod'
          })
          return true
        }
      }
      // This path is currently not taken.
      return false
    }
    /**
     * Verify for inline function handler.
     * @param {ArrowFunctionExpression | FunctionExpression} node
     * @param {HandlerKind} kind
     * @returns {boolean} Returns `true` if reported.
     */
    function verifyForInlineFunction(node, kind) {
      switch (kind) {
        case 'method': {
          return verifyCanUseMethodHandlerForInlineFunction(node)
        }
        case 'inline': {
          reportCanUseInlineHandlerForInlineFunction(node)
          return true
        }
      }
      return false
    }

    /**
     * Get token information for the given VExpressionContainer node.
     * @param {VExpressionContainer} node
     */
    function getVExpressionContainerTokenInfo(node) {
      const sourceCode = context.getSourceCode()
      const tokenStore = sourceCode.parserServices.getTemplateBodyTokenStore()
      const tokens = tokenStore.getTokens(node, {
        includeComments: true
      })
      const firstToken = tokens[0]
      const lastToken = tokens[tokens.length - 1]

      const hasQuote = isQuote(firstToken)
      /** @type {Range} */
      const rangeWithoutQuotes = hasQuote
        ? [firstToken.range[1], lastToken.range[0]]
        : [firstToken.range[0], lastToken.range[1]]

      return {
        rangeWithoutQuotes,
        get hasComment() {
          return tokens.some(
            (token) => token.type === 'Block' || token.type === 'Line'
          )
        },
        hasQuote
      }
    }

    /**
     * Checks whether the given node refers to a variable of the element.
     * @param {Expression | VOnExpression} node
     */
    function hasReferenceUpperElementVariable(node) {
      for (const element of upperElements) {
        for (const vv of element.variables) {
          for (const reference of vv.references) {
            const { range } = reference.id
            if (node.range[0] <= range[0] && range[1] <= node.range[1]) {
              return true
            }
          }
        }
      }
      return false
    }
    /**
     * Check if `v-on:click="foo()"` can be converted to `v-on:click="foo"` and report if it can.
     * @param {VOnExpression} node
     * @returns {boolean} Returns `true` if reported.
     */
    function verifyCanUseMethodHandlerForInlineHandler(node) {
      const { rangeWithoutQuotes, hasComment } =
        getVExpressionContainerTokenInfo(node.parent)
      if (ignoreIncludesComment && hasComment) {
        return false
      }

      const idCallExpr = getIdentifierCallExpression(node)
      if (
        (!idCallExpr || idCallExpr.arguments.length > 0) &&
        hasReferenceUpperElementVariable(node)
      ) {
        // It cannot be converted to method because it refers to the variable of the element.
        // e.g. <template v-for="e in list"><button @click="foo(e)" /></template>
        return false
      }

      context.report({
        node,
        messageId: idCallExpr
          ? 'preferMethodOverInline'
          : 'preferMethodOverInlineWithoutIdCall',
        fix: (fixer) => {
          if (
            hasComment /* The statement contains comment and cannot be fixed. */ ||
            !idCallExpr /* The statement is not a simple identifier call and cannot be fixed. */ ||
            idCallExpr.arguments.length > 0
          ) {
            return null
          }
          const paramCount = methodParamCountMap.get(idCallExpr.callee.name)
          if (paramCount != null && paramCount > 0) {
            // The behavior of target method can change given the arguments.
            return null
          }
          return fixer.replaceTextRange(
            rangeWithoutQuotes,
            context.getSourceCode().getText(idCallExpr.callee)
          )
        }
      })
      return true
    }
    /**
     * Check if `v-on:click="() => foo()"` can be converted to `v-on:click="foo"` and report if it can.
     * @param {ArrowFunctionExpression | FunctionExpression} node
     * @returns {boolean} Returns `true` if reported.
     */
    function verifyCanUseMethodHandlerForInlineFunction(node) {
      const { rangeWithoutQuotes, hasComment } =
        getVExpressionContainerTokenInfo(
          /** @type {VExpressionContainer} */ (node.parent)
        )
      if (ignoreIncludesComment && hasComment) {
        return false
      }

      /** @type {CallExpression & {callee: Identifier} | null} */
      let idCallExpr = null
      if (node.body.type === 'BlockStatement') {
        idCallExpr = getIdentifierCallExpression(node.body)
      } else if (isIdentifierCallExpression(node.body)) {
        idCallExpr = node.body
      }
      if (
        (!idCallExpr || !isSameParamsAndArgs(idCallExpr)) &&
        hasReferenceUpperElementVariable(node)
      ) {
        // It cannot be converted to method because it refers to the variable of the element.
        // e.g. <template v-for="e in list"><button @click="() => foo(e)" /></template>
        return false
      }

      context.report({
        node,
        messageId: idCallExpr
          ? 'preferMethodOverInlineFunction'
          : 'preferMethodOverInlineFunctionWithoutIdCall',
        fix: (fixer) => {
          if (
            hasComment /* The function contains comment and cannot be fixed. */ ||
            !idCallExpr /* The function is not a simple identifier call and cannot be fixed. */
          ) {
            return null
          }
          if (!isSameParamsAndArgs(idCallExpr)) {
            // It is not a call with the arguments given as is.
            return null
          }
          const paramCount = methodParamCountMap.get(idCallExpr.callee.name)
          if (
            paramCount != null &&
            paramCount !== idCallExpr.arguments.length
          ) {
            // The behavior of target method can change given the arguments.
            return null
          }
          return fixer.replaceTextRange(
            rangeWithoutQuotes,
            context.getSourceCode().getText(idCallExpr.callee)
          )
        }
      })
      return true

      /**
       * Checks whether parameters are passed as arguments as-is.
       * @param {CallExpression} expression
       */
      function isSameParamsAndArgs(expression) {
        return (
          node.params.length === expression.arguments.length &&
          node.params.every((param, index) => {
            if (param.type !== 'Identifier') {
              return false
            }
            const arg = expression.arguments[index]
            if (!arg || arg.type !== 'Identifier') {
              return false
            }
            return param.name === arg.name
          })
        )
      }
    }
    /**
     * Report `v-on:click="foo()"` can be converted to `v-on:click="()=>foo()"`.
     * @param {VOnExpression} node
     * @returns {void}
     */
    function reportCanUseInlineFunctionForInlineHandler(node) {
      context.report({
        node,
        messageId: 'preferInlineFunctionOverInline',
        *fix(fixer) {
          const has$Event = $eventIdentifiers.some(
            ({ range }) =>
              node.range[0] <= range[0] && range[1] <= node.range[1]
          )
          if (has$Event) {
            /* The statements contains $event and cannot be fixed. */
            return
          }
          const { rangeWithoutQuotes, hasQuote } =
            getVExpressionContainerTokenInfo(node.parent)
          if (!hasQuote) {
            /* The statements is not enclosed in quotes and cannot be fixed. */
            return
          }
          yield fixer.insertTextBeforeRange(rangeWithoutQuotes, '() => ')
          const sourceCode = context.getSourceCode()
          const tokenStore =
            sourceCode.parserServices.getTemplateBodyTokenStore()
          const firstToken = tokenStore.getFirstToken(node)
          const lastToken = tokenStore.getLastToken(node)
          if (firstToken.value === '{' && lastToken.value === '}') return
          if (
            lastToken.value !== ';' &&
            node.body.length === 1 &&
            node.body[0].type === 'ExpressionStatement'
          ) {
            // it is a single expression
            return
          }
          yield fixer.insertTextBefore(firstToken, '{')
          yield fixer.insertTextAfter(lastToken, '}')
        }
      })
    }
    /**
     * Report `v-on:click="() => foo()"` can be converted to `v-on:click="foo()"`.
     * @param {ArrowFunctionExpression | FunctionExpression} node
     * @returns {void}
     */
    function reportCanUseInlineHandlerForInlineFunction(node) {
      // If a function has one parameter, you can turn it into an inline handler using $event.
      // If a function has two or more parameters, it cannot be easily converted to an inline handler.
      // However, users can use inline handlers by changing the payload of the component's custom event.
      // So we report it regardless of the number of parameters.

      context.report({
        node,
        messageId:
          node.params.length > 1
            ? 'preferInlineOverInlineFunctionWithMultipleParams'
            : 'preferInlineOverInlineFunction',
        fix:
          node.params.length > 0
            ? null /* The function has parameters and cannot be fixed. */
            : (fixer) => {
                let text = context.getSourceCode().getText(node.body)
                if (node.body.type === 'BlockStatement') {
                  text = text.slice(1, -1) // strip braces
                }
                return fixer.replaceText(node, text)
              }
      })
    }

    return utils.defineTemplateBodyVisitor(
      context,
      {
        VElement(node) {
          upperElements.add(node)
        },
        'VElement:exit'(node) {
          upperElements.delete(node)
        },
        /** @param {VExpressionContainer} node */
        "VAttribute[directive=true][key.name.name='on'][key.argument!=null] > VExpressionContainer.value:exit"(
          node
        ) {
          const expression = node.expression
          if (!expression) {
            return
          }
          switch (expression.type) {
            case 'VOnExpression': {
              // e.g. v-on:click="foo()"
              if (allows[0] === 'inline') {
                return
              }
              for (const allow of allows) {
                if (verifyForInlineHandler(expression, allow)) {
                  return
                }
              }
              break
            }
            case 'Identifier': {
              // e.g. v-on:click="foo"
              if (allows[0] === 'method') {
                return
              }
              for (const allow of allows) {
                if (reportForMethodHandler(expression, allow)) {
                  return
                }
              }
              break
            }
            case 'ArrowFunctionExpression':
            case 'FunctionExpression': {
              // e.g. v-on:click="()=>foo()"
              if (allows[0] === 'inline-function') {
                return
              }
              for (const allow of allows) {
                if (verifyForInlineFunction(expression, allow)) {
                  return
                }
              }
              break
            }
            default: {
              return
            }
          }
        },
        ...(allows.includes('inline-function')
          ? // Collect $event identifiers to check for side effects
            // when converting from `v-on:click="foo($event)"` to `v-on:click="()=>foo($event)"` .
            {
              'Identifier[name="$event"]'(node) {
                $eventIdentifiers.push(node)
              }
            }
          : {})
      },
      allows.includes('method')
        ? // Collect method definition with params information to check for side effects.
          // when converting from `v-on:click="foo()"` to `v-on:click="foo"`, or
          // converting from `v-on:click="() => foo()"` to `v-on:click="foo"`.
          utils.defineVueVisitor(context, {
            onVueObjectEnter(node) {
              for (const method of utils.iterateProperties(
                node,
                new Set(['methods'])
              )) {
                if (method.type !== 'object') {
                  // This branch is usually not passed.
                  continue
                }
                const value = method.property.value
                if (
                  value.type === 'FunctionExpression' ||
                  value.type === 'ArrowFunctionExpression'
                ) {
                  methodParamCountMap.set(
                    method.name,
                    value.params.some((p) => p.type === 'RestElement')
                      ? Number.POSITIVE_INFINITY
                      : value.params.length
                  )
                }
              }
            }
          })
        : {}
    )
  }
}