Middleware documentation / Guide

[jdevcs]

• web3 middleware usecase test / feedback: Check with real usecase if any breaking changes are required before merging and release
• publish middleware ( include in next release )

Related feature work can be found at:
#7134
#7002
#7003

[jdevcs]

Create plugin developers Guide for Middleware implementation:
Types of Middleware:
1 - Request Middleware: can be use to modify request before sent to RPC node by web3.js and/or modify response before returning back to web3.js, steps:

• Middleware Interface and methods specs:

  web3.js/packages/web3-core/src/types.ts

  Line 39 in 9afaa61

  export interface RequestManagerMiddleware<API> {

  
  ( examples are linked in following steps)
  A. Implement middleware.
  B. Create its instance based on your logic in plugin
  C. set middleware in link method
  Once its set , any JSON RPC request from all web3 packages will go through this middleware

2- Transaction Middleware: ( works for Eth and Contracts package )
steps:

• Middleware Interface and methods specs:

  web3.js/packages/web3-eth/src/types.ts

  Line 100 in 9afaa61

  export interface TransactionMiddleware{

  
  A. Example implementation
  B. Create Instance in plugin example
  C. Set Transaction middleware example
  Once its set , web3 will call Transaction middleware before signing transaction.

Some code snippets in tests:
Requests middleware:

web3.js/tools/web3-plugin-example/test/unit/request_manager_middleware.test.ts

Line 24 in 9afaa61

const web3 = new Web3('http://127.0.0.1:8545');

Eth Transaction middleware:

web3.js/tools/web3-plugin-example/test/unit/transaction_middleware.test.ts

Line 26 in 9afaa61

const web3 = new Web3('http://127.0.0.1:8545');

Contract Transaction middleware:

web3.js/tools/web3-plugin-example/test/unit/contract_transaction_middleware.test.ts

Line 30 in 9afaa61

const plugin: TransactionMiddlewarePlugin = new TransactionMiddlewarePlugin();

[danforbes]

@jdevcs why is it necessary to add a new property to the plugin class AND register the plugin in the link method?

[jdevcs]

@jdevcs why is it necessary to add a new property to the plugin class AND register the plugin in the link method?

@danforbes add a new property to the plugin class is not necessary, middleware can be injected in plugin, or plugin can have access to middleware via other ways,

but registering (Transaction or Request ) middleware in link method is necessary because it will set middleware via web3-context to Web3-Eth & Web3-Contract or Web3-Request-Manager, so when normal request is sent via other web3 packages it can see if middleware is there or not for usage.