Add concurrency explanation -> FAQ

[jablko]

I ran into this issue here:

$ lerna run test-types
lerna notice cli v3.22.1
lerna info ci enabled
lerna info Executing command in 8 packages: "yarn run test-types"
lerna ERR! yarn run test-types exited 1 in '@mdx-js/react'
lerna ERR! yarn run test-types stdout:
$ dtslint types
Installing to /home/runner/.dts/typescript-installs/3.8...
Installed!

Installing to /home/runner/.dts/typescript-installs/4.0...
Installed!

Installing to /home/runner/.dts/typescript-installs/4.2...
Installed!

Installing to /home/runner/.dts/typescript-installs/4.3...
Installed!

info Visit https://yarnpkg.com/en/docs/cli/run for documentation about this command.

lerna ERR! yarn run test-types stderr:
Error: Cannot find module '/home/runner/.dts/typescript-installs/4.5/node_modules/typescript'
Require stack:
- /home/runner/work/mdx/mdx/node_modules/dtslint/bin/lint.js
- /home/runner/work/mdx/mdx/node_modules/dtslint/bin/index.js
    at Function.Module._resolveFilename (node:internal/modules/cjs/loader:933:15)
    at Function.Module._load (node:internal/modules/cjs/loader:778:27)
    at Module.require (node:internal/modules/cjs/loader:1005:19)
    at require (node:internal/modules/cjs/helpers:94:18)
    at testDependencies (/home/runner/work/mdx/mdx/node_modules/dtslint/bin/lint.js:66:16)
    at /home/runner/work/mdx/mdx/node_modules/dtslint/bin/lint.js:26:28
    at Generator.next (<anonymous>)
    at /home/runner/work/mdx/mdx/node_modules/dtslint/bin/lint.js:8:71
    at new Promise (<anonymous>)
    at __awaiter (/home/runner/work/mdx/mdx/node_modules/dtslint/bin/lint.js:4:12)
error Command failed with exit code 1.

The failed invocation installed 3.8, 4.0, etc., a concurrent invocation installed 3.9, 4.5, etc. The failed invocation found the 4.5 directory but didn't wait for the 4.5 installation to complete and failed as a result (I surmise).

Solved with lerna --concurrency 1 run .... I suspect this is also the cause behind mdx-js/mdx#1172 and #267.

Fixes #267

[jablko]

Package lock files such as yarn.lock and package-lock.json may cause this issue because of our github dependency on "definitelytyped-header-parser": "github:Microsoft/definitelytyped-header-parser#production", which contains the list of typescript versions to install. To fix this, try deleting your lock file and re-installing.

Separate topic but can this text be removed since 5e0f2e5, or #287?

[sandersn]

I think you can still run into the problem, but the explanation should just be "Your dependencies may be out of date."

package-lock.json is checked into dtslint but not Definitely Typed, so maybe the solution can just be npm ci? But only if you're doing it from this repo and not Definitely Typed.

[sandersn]

Thanks for the update. What do you think about the suggested change to the previous line?

[sandersn]

I think you can still run into the problem, but the explanation should just be "Your dependencies may be out of date."

package-lock.json is checked into dtslint but not Definitely Typed, so maybe the solution can just be npm ci? But only if you're doing it from this repo and not Definitely Typed.

[jablko]

Thanks for the update. What do you think about the suggested change to the previous line?

Sounds good 👍 I've updated that line.

This FAQ is to do with installing one list of TypeScript versions, and testing another, which can only happen if you end up with two different @definitelytyped/typescript-versions (I think). I haven't investigated the current dtslint/dtslint-runner/typescript-versions relationship to confirm how that could happen ...

I do vaguely recollect encountering this in the past ... There are child worker processes involved if I remember, so maybe somewhere in there the process doing the installing uses one node_modules and the one doing the testing uses another ...