Hardhat-deploy: Using Open Zeppelin Upgrade Plugin

Hello @Remscar, it would definitely be great.
Meanwhile, I developed a "workaround" plugin to do it, I copied some code from @openzeppelin/upgrade-core library.
It's a bit ugly but it can do the work ( use it at your own risk ).

Import this file ( after importing hardhat-deploy ) in the hardhat-config.js :

const { extendEnvironment } = require("hardhat/config")
const AdminUpgradeabilityProxy = require("@openzeppelin/upgrades-core/artifacts/contracts/proxy/AdminUpgradeabilityProxy.sol/AdminUpgradeabilityProxy.json")
const ProxyAdmin = require("@openzeppelin/upgrades-core/artifacts/contracts/proxy/ProxyAdmin.sol/ProxyAdmin.json")
const { assertUpgradeSafe, getVersion, getUnlinkedBytecode } = require("@openzeppelin/upgrades-core")
const { readValidations } = require("@openzeppelin/hardhat-upgrades/dist/validations")

const getSigner = async address => {
  const signers = await hre.ethers.getSigners()
  return signers.find(signer => signer.address === address)
}

const getInitializerData = (ImplFactory, args = [], initializer) => {
  if (initializer === false) {
    return "0x"
  }
  const allowNoInitialization = initializer === undefined && args.length === 0
  initializer = initializer ?? "initialize"
  try {
    const fragment = ImplFactory.interface.getFunction(initializer)
    return ImplFactory.interface.encodeFunctionData(fragment, args)
  } catch (e) {
    if (e instanceof Error) {
      if (allowNoInitialization && e.message.includes("no matching function")) {
        return "0x"
      }
    }
    throw e
  }
}

const deployProxyAdmin = async (owner) => {
  const { deployments } = hre
  const { deploy } = deployments
  return await deploy("ProxyAdmin", {
    contract: ProxyAdmin,
    from: owner,
    log: true,
  })
}

const deployOrUpgrade = async (firstImplName, opts, { initializer, postUpgrade, upgrades }) => {
  const { deployments } = hre
  const { deploy } = deployments
  let proxyAdmin
  try {
    proxyAdmin = await deployments.get("ProxyAdmin")
  } catch (error) {
    proxyAdmin = await deployProxyAdmin(opts.from)
  }
  const proxyName = `${firstImplName}Proxy`
  const firstImpl = await deploy(firstImplName, opts)
  const initData = getInitializerData(
    await ethers.getContractFactory(firstImplName),
    initializer && initializer.args ? initializer.args : [],
    initializer ? initializer.method : false
  )
  const proxy = await deploy(proxyName, {
    contract: AdminUpgradeabilityProxy,
    from: opts.from,
    log: true,
    args: [firstImpl.address, proxyAdmin.address, initData],
  })

  if (upgrades && upgrades.length > 0) {
    let previousImplName, newImplName
    if (upgrades.length === 1) {
      previousImplName = firstImplName
      newImplName = upgrades[0]
    } else {
      newImplName = upgrades.pop()
      previousImplName = upgrades.pop()
      for (oldUpgrade in upgrades) {
        // unsure previous upgrades exists
        await deployments.get(upgrades[oldUpgrade])
      }
    }
    if (previousImplName === newImplName) throw new Error("Same implementation, can't upgrade.")
    const newImplFactory = await ethers.getContractFactory(newImplName)
    const validations = await readValidations(hre)
    const unlinkedBytecode = getUnlinkedBytecode(validations, newImplFactory.bytecode)
    const version = getVersion(unlinkedBytecode, newImplFactory.bytecode)
    assertUpgradeSafe(validations, version, {
      unsafeAllowCustomTypes: false,
      unsafeAllowLinkedLibraries: false,
    })

    const signer = await getSigner(opts.from)
    const proxyAdminContract = await ethers.getContractAt(proxyAdmin.abi, proxyAdmin.address, signer)
    const previousImpl = await deployments.get(previousImplName)
    const actualImpl = await proxyAdminContract.getProxyImplementation(proxy.address)
    const newImpl = await deploy(newImplName, {
      from: opts.from,
      log: true,
    })
    if (newImpl.newlyDeployed)
      if (actualImpl == previousImpl.address) {
        console.log(`Upgrading from ${previousImplName} to ${newImplName}`)
        if (postUpgrade && postUpgrade.method && postUpgrade.args) {
          const upgradeData = getInitializerData(await ethers.getContractFactory(newImplName), postUpgrade.args, postUpgrade.method)
          await proxyAdminContract.upgradeAndCall(proxy.address, newImpl.address, upgradeData)
        } else await proxyAdminContract.upgrade(proxy.address, newImpl.address)
      } else throw new Error(`Proxy is actually pointing on: ${actualImpl}`)
  }
  return proxy
}

extendEnvironment(hre => {
  hre.myPlugin = {
    deployOrUpgrade,
  }
})

Usage :

module.exports = async ({ getNamedAccounts, myPlugin }) => {
  const { deployer } = await getNamedAccounts()
  // This will deploy the "Contract" with a proxy and  a proxyAdmin if it doesn't exist.
  const proxy = await myPlugin.deployOrUpgrade(
    "Contract",
    { from: deployer, log: true },
    {
      initializer: { method: "initialize", args: [] },
      // bellow attributes for upgrading
      postUpgrade: { method: "postUpgrade", args: [] }, // method to  exec after upgrade
      upgrades: ["ContractV2", "ContractV3"], // you should keep the list of upgrades and add the new one at  the last
    }
  )
}

There is now a builtin way to use Openzeppelin Transparent Proxy. I ll close this issue