method-override.ts

type MethodOverrideOptions = {
  // Default is 'form' and the value is `_method`
  form?: string
  header?: string
  query?: string
}

const DEFAULT_METHOD_FORM_NAME = '_method'

const methodOverride = (options?: MethodOverrideOptions): MiddlewareHandler =>
  async function methodOverride(c, next) {
    // Method override by form
    if (!options || options.form || !(options.form || options.header || options.query)) {
      const methodFormName = options?.form || DEFAULT_METHOD_FORM_NAME
      const contentType = c.req.header('content-type')
      if (!(contentType === 'multipart/form-data' || contentType === 'application/x-www-form-urlencoded')) {
        return await next()
      }
      const clonedRequest = c.req.raw.clone()
      const newRequest = clonedRequest.clone()
      const form = await clonedRequest.formData()
      const method = form.get(methodFormName)
      if (method) {
        const newForm = await newRequest.formData()
        newForm.delete(methodFormName)
        const newHeaders = new Headers(clonedRequest.headers)
        newHeaders.delete('content-type')
        newHeaders.delete('content-length')
        const request = new Request(c.req.url, {
          body: newForm,
          headers: newHeaders,
          method
        })
        return app.fetch(request, c.env, c.executionCtx)
      }
    }
    // Method override by header
    else if (options.header) {
      const headerName = options.header
      const method = c.req.header(headerName)
      if (method) {
        const newHeaders = new Headers(c.req.raw.headers)
        newHeaders.delete(headerName)
        const request = new Request(c.req.raw, {
          headers: newHeaders,
          method
        })
        return app.fetch(request, c.env, c.executionCtx)
      }
    }
    // Method override by query
    else if (options.query) {
      const queryName = options.query
      const method = c.req.query(queryName)
      if (method) {
        const url = new URL(c.req.url)
        url.searchParams.delete(queryName)
        const request = new Request(url.toString(), {
          body: c.req.raw.body,
          headers: c.req.raw.headers,
          method
        })
        return app.fetch(request, c.env, c.executionCtx)
      }
    }
    await next()
  }

Thanks for the explanation about the content-type, I understand. Thanks!

@usualoma

Created the PR! honojs/hono#2420