Heroku 64-bit Ubuntu 14.04 + yarn: Cannot find module '../build/Release/sharp.node'

When attempting to build a project on heroku we are experiencing an issue where sharp.node is not being found. Below is the heroku build output:

Downloading and installing node 6.9.1...
       Using default npm version: 3.10.8
       Downloading and installing yarn (0.20.3)...
       Installed yarn 0.20.3
-----> Restoring cache
       Loading 2 from cacheDirectories (default):
       - node_modules
       - bower_components (not cached - skipping)
-----> Building dependencies
       Installing node modules (yarn.lock)
       yarn install v0.20.3
       [1/4] Resolving packages...
       [2/4] Fetching packages...
       warning fsevents@1.0.17: The platform "linux" is incompatible with this module.
       info "fsevents@1.0.17" is an optional dependency and failed compatibility check. Excluding it from installation.
       [3/4] Linking dependencies...
       warning "redux-form@5.2.5" has incorrect peer dependency "react-redux@^3.0.0 || ^4.0.0".
       [4/4] Building fresh packages...
       $ gulp build
       module.js:471
       throw err;
       ^
       
       Error: Cannot find module '../build/Release/sharp.node'
       at Function.Module._resolveFilename (module.js:469:15)
       at Function.Module._load (module.js:417:25)
       at Module.require (module.js:497:17)
       at require (internal/module.js:20:19)
       at Object.<anonymous> (/tmp/build_a0cdb656013074c78176c1bdebea3455/Lostmyname-website-d9b76f1e1644504c47a0c934bed5fd92db728cb1/node_modules/sharp/lib/constructor.js:8:15)
       at Module._compile (module.js:570:32)
       at Object.Module._extensions..js (module.js:579:10)
       at Module.load (module.js:487:32)
       at tryModuleLoad (module.js:446:12)
       at Function.Module._load (module.js:438:3)
       error Command failed with exit code 1.
       info Visit https://yarnpkg.com/en/docs/cli/install for documentation about this command.
-----> Build failed

[griffinpp]

We were experiencing this issue, and got things working again by setting NODE_MODULES_CACHE to false (heroku -a <appname> config:set NODE_MODULES_CACHE=false).

Our best guess, based on some rudimentary testing, is that heroku is not able or not configured to cache binary files. So if caching is enabled, an initial deploy works fine, but a second deploy will attempt to use the cached modules, which do not contain the necessary binary files. Disabling caching forces the application to always use the correct, uncached node_modules directory.

[lovell]

Docs updated in 5e015cc, thanks all.