Not fully compatible with yarn package manager

[amokrushin]

yarn add exiftool-vendored
node index.js
OK

yarn add anything-else
node index.js
Error: Cannot find module 'exiftool-vendored.pl'
    at Function.Module._resolveFilename (module.js:470:15)
    at Function.Module._load (module.js:418:25)
    at Module.require (module.js:498:17)
    at require (internal/module.js:20:19)
    at Object.<anonymous> (/srv/nodejs/test-exiftool/node_modules/exiftool-vendored/dist/ExifTool.js:17:20)
    at Module._compile (module.js:571:32)
    at Object.Module._extensions..js (module.js:580:10)
    at Module.load (module.js:488:32)
    at tryModuleLoad (module.js:447:12)
    at Function.Module._load (module.js:439:3)

index.js includes only import of exiftool-vendored module

Works ok only on clean install or if exiftool-vendored.pl explicitly added as a package dependency.

This does not cause much inconvenience in a case of exiftool-vendored is a direct dependency. But it is not so if there are intermediate dependencies.
For example module-a -> module-b -> exiftool-vendored. Whenever a module-a adds a new dependency, mobule-b will throw an error.

[mceachen]

This is a bug in yarn's interaction with platform-dependent-modules. If you know of another way to have platform-specific dependencies, I'd appreciate any suggestions.

[amokrushin]

It's not a bug of yarn, it is an expected behaviour. yarn add command automatically removes all not explicitly defined modules.
You already defined an os section in exiftool-vendored.exe and exiftool-vendored.pl modules, so you should be able to remove your platform-dependent-modules dependency and replace package.json's config section with

"optionalDependencies": {
    "exiftool-vendored.pl": "10.51.0",
    "exiftool-vendored.exe": "10.51.0"
}

Package managers (npm or yarn) will not install modules which aren't compatible with the current platform os. So on a target platform only one of that modules will be installed.
But I don't know has this solution any side effect or not.

[mceachen]

I actually used this approach in versions prior to v1.5.3, see 3690c73#diff-b9cfc7f2cdf78a7f4b91a753d10865a2.

This post highlights a defect with this approach: if the dependency fails to install, npm just reports it as a warning and carries on. This issue in yarn is somewhat related.

[amokrushin]

I don't understand what the problem was with that solution.

It seems working as expected with both of yarn and npm:

am@135775:/srv/nodejs/qaa1nd07/base$ yarn
yarn install v0.24.5
info No lockfile found.
[1/4] Resolving packages...
[2/4] Fetching packages...
warning qaa1nd07-dep-win32@0.1.1: The platform "linux" is incompatible with this module.
info "qaa1nd07-dep-win32@0.1.1" is an optional dependency and failed compatibility check. Excluding it from installation.
[3/4] Linking dependencies...
[4/4] Building fresh packages...
success Saved lockfile.
Done in 0.37s.

am@135775:/srv/nodejs/qaa1nd07/base$ npm i
qaa1nd07-base@0.1.0 /srv/nodejs/qaa1nd07/base
└── qaa1nd07-dep-linux@0.1.1

npm WARN optional SKIPPING OPTIONAL DEPENDENCY: qaa1nd07-dep-win32@^0.1.1 (node_modules/qaa1nd07-dep-win32):
npm WARN notsup SKIPPING OPTIONAL DEPENDENCY: Unsupported platform for qaa1nd07-dep-win32@0.1.1: wanted {"os":"win32","arch":"any"} (current: {"os":"linux","arch":"x64"})
npm WARN qaa1nd07-base@0.1.0 No description
npm WARN qaa1nd07-base@0.1.0 No repository field.

If only problew was

Making all versions of the dependency optional means that if your installation fails for a legitimate reason, it will silently skip installation and you will be missing a dependency you really need.

Then postinstall hook can verify that one was installed and throw error if not.

[mceachen]

NICE! I didn't even think about doing a validation step in the postinstall. Do you want to make a PR for this, or wait for me to do it?

Thanks!

[amokrushin]

PR is ready

[mceachen]

Thanks for your help. Travis now runs the builds with yarn, and I'll release this version tomorrow.