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Overview

This feature is implemented according to the GraphQL multipart request specification, utilizing the multipart/form-data content type. Cosmo supports both single and multiple file uploads, but batch uploads are not supported. The router can be configured for file uploads with these options.

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Multipart Request Structure

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operations

A JSON-encoded operations object with files replaced by null. This object defines the GraphQL query or mutation to be executed, along with the necessary variables.

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map

A JSON-encoded map indicating where files appear in the operations. For each file, the key is the file’s multipart form field name, and the value is an array of operations paths. This map ensures the correct association between the files and their respective variables in the GraphQL operation.

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File Fields

Each file extracted from the operations object is assigned a unique, arbitrary field name. These fields are included in the multipart form data and correspond to the file paths specified in the map.

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Sample Setup

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Define Custom Scalar

You need to define a custom scalar Upload in your schema. This scalar will be used for the field type where you intend to upload files. 
scalar Upload

type Mutation {
  singleUpload(file: Upload!): Boolean!
  multipleUpload(files: [Upload!]!): Boolean!
}

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Single File Upload

To upload a single file, use the following curl command: 
curl localhost:3002/graphql \
  -F operations='{ "query": "mutation ($file: Upload!) { singleUpload(file: $file) }", "variables": { "file": null } }' \
  -F map='{ "0": ["variables.file"] }' \
  -F 0=@a.txt
This command sends a multipart request where:
  • operations defines the GraphQL mutation with the file variable set to null.
  • map associates the form field 0 with variables.file.
  • 0=@a.txt uploads the file a.txt with the form field name 0.

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Multiple Files Upload

To upload multiple files, use the following curl command: 
curl localhost:3002/graphql \
  -F operations='{ "query": "mutation($files: [Upload!]!) { multipleUpload(files: $files) }", "variables": { "files": [null, null] } }' \
  -F map='{ "0": ["variables.files.0"], "1": ["variables.files.1"] }' \
  -F 0=@a.txt \
  -F 1=@b.txt
This command sends a multipart request where:
  • operations defines the GraphQL mutation with the files variable set to an array of null values.
  • map associates the form fields 0 and 1 with variables.files.0 and variables.files.1 respectively.
  • 0=@a.txt and 1=@b.txt upload the files a.txt and b.txt with form field names 0 and 1.
By following these examples, you can configure your router to handle single and multiple file uploads effectively using GraphQL multipart requests. For more details, refer to the GraphQL multipart request specification.