Improved documentation and error reporting to work around macos DYLD_LIBRARY_PATH requirements (#42)

Author: josephg

README.md

@@ -28,6 +28,10 @@ To connect to a remote cluster you need:
 - A copy of the client library with matching major and minor version numbers. You really only need the `libfdb_c` dynamic library file to connect ([available on the fdb downloads page](https://www.foundationdb.org/download/)). But its usually easier to just install the fdb client library for your platform. See [Notes on API versions](#notes-on-api-versions) below for more information.
 - A copy of the `fdb.cluster` file for your database cluster. If you have installed foundationdb on your local machine in the default location, a copy of this file will be discovered and used automatically.
 
+#### Step 1b (macos only)
+
+If you're on a mac, add `export DYLD_LIBRARY_PATH=/usr/local/lib` to your .zshrc or .bash_profile. This is [needed due to macos binary sandboxing](https://github.com/josephg/node-foundationdb/issues/42).
+
 #### Step 2
 
 ```

lib/native.ts

@@ -1,3 +1,4 @@
+import {platform} from 'os'
 import path = require('path')
 
 import FDBError from './error'
@@ -119,6 +120,20 @@ try {
 } catch (e) {
   console.error('Could not load native module. Make sure the foundationdb client is installed and')
   console.error('(on windows) in your PATH. https://www.foundationdb.org/download/')
+
+  // This is way more involved than it needs to be, but error messages are important.
+  if (platform() === 'darwin') {
+    const ldLibraryPath = process.env['DYLD_LIBRARY_PATH'] || ''
+    if (!ldLibraryPath.includes('/usr/local/lib')) {
+      const configFile = process.env['SHELL'] === '/bin/zsh' ? '.zshrc' : '.bash_profile'
+
+      console.error()
+      console.error('MacOS note: You also need to set DYLD_LIBRARY_PATH="/usr/local/lib" due to notarization. Run:\n')
+      console.error(`  echo \'export DYLD_LIBRARY_PATH="/usr/local/lib"\' >> ~/${configFile}`)
+      console.error(`  source ~/${configFile}`)
+      console.error('\nThen retry. See https://github.com/josephg/node-foundationdb/issues/42 for details.\n\n')
+    }
+  }
   throw e
 }