Implement type checking

[turadg]

This repo has a TypeScript config (https://github.com/Agoric/dapp-treasury/blob/main/ui/jsconfig.json) but there's no command that uses it to verify types check out.

Acceptance criteria

• dev command to check types
• type errors fail CI

Examples of errors present

cd ui
yarn tsc -p jsconfig.json
# Found 35 errors in 21 files.

Duplicate ambients

../../agoric-sdk/node_modules/@endo/promise-kit/index.js:4:23 - error TS4090: Conflicting definitions for 'ses' found at '/opt/agoric/agoric-sdk/node_modules/ses/index.d.ts' and '/opt/agoric/dapp-treasury/node_modules/ses/index.d.ts'. Consider installing a specific version of this library to resolve the conflict.
  The file is in the program because:
    Imported via 'ses' from file '/opt/agoric/dapp-treasury/ui/src/install-ses-lockdown.js' with packageId 'ses/[email protected]'
    Type library referenced via 'ses' from file '/opt/agoric/dapp-treasury/ui/node_modules/@endo/eventual-send/src/handled-promise.js' with packageId 'ses/[email protected]'
    Type library referenced via 'ses' from file '/opt/agoric/agoric-sdk/node_modules/@endo/promise-kit/index.js' with packageId 'ses/[email protected]'

4 /// <reference types="ses"/>
                        ~~~

  src/install-ses-lockdown.js:1:8
    1 import 'ses';
             ~~~~~
    File is included via import here.
  node_modules/@endo/eventual-send/src/handled-promise.js:2:23
    2 /// <reference types="ses" />
                            ~~~
    File is included via type library reference here.

Missing types

../node_modules/@endo/captp/src/captp.js:32:15 - error TS2304: Cannot find name 'TrapGuest'.

32  * @property {TrapGuest} trapGuest if specified, enable this CapTP (guest) to
                 ~~~~~~~~~

../node_modules/@endo/captp/src/captp.js:35:15 - error TS2304: Cannot find name 'TrapHost'.

35  * @property {TrapHost} trapHost if specified, enable this CapTP (host) to serve
                 ~~~~~~~~

../node_modules/@endo/captp/src/captp.js:124:27 - error TS2304: Cannot find name 'CapTPSlot'.

124   /** @type {WeakMap<any, CapTPSlot>} */
                              ~~~~~~~~~

[samsiegart]

Do you have any opinions on whether we should do this as a separate yarn command, or part of build/lint/test/etc.?

[turadg]

opinions

Almost always happy to opine :)

To make it easy for people to come into repo and be productive, I think the commands they're used to should work. E.g. running yarn tsc anywhere in the repo should do a typecheck because that's the TypeScript command for doing a typecheck.

Whether that gets run in a yarn lint, I'm weaker on. My mental model is that linting is disjoint from formatting and type checking, but I get that for some it encompasses all that. In sdk yarn lint runs both eslint and tsc. Here's how I think of these:

• yarn format normalize anything that can't affect semantics (e.g. whitespace)
• yarn lint static analysis of things that could require semantic change
• yarn test execute code to observe its runtime

By that logic a typecheck wouldn't go under yarn test. Though I did that in https://github.com/endojs/endo/blob/88893be94254fca1821944fa730613cbdb29fbfd/packages/ses/package.json#L58 and maybe I should change it.

[turadg]

Upped priority to MN-1 because it'll help us get there faster by preventing bugs like Agoric/agoric-sdk#5260 (comment)

[turadg]

There's a PR to enable this #120 but in its current state it passes CI by no longer resolving many types, leaving them as implicit any.

The motivation for this issue is that we can detect type incompatibilities during the test-dapp-treasury integration test. If we don't have types working correctly then CI isn't worth enabling.

So I'm expanding the scope of this to include that. I don't yet know what it'll take so I'm raising the estimate to be conservative. We'll know the costs better after discussing with @mhofman .

I'm leaving the MN-1 release tag here but I expect it may be deferred to 1.1.