Fix #2669 & #2396 - Failure to start Neovim on OSX 10.14 Mojave (#2682)

* Set 'LANG' environment variable on Mac if not set to workaround crash

* Fix lint

browser/src/Plugins/Api/Process.ts

@@ -155,14 +155,28 @@ export class Process implements Oni.Process {
             existingPath = process.env.Path || process.env.PATH
         }
 
+        const additionalEnvironmentVariables =
+            configuration.getValue("environment.additionalVariables") || {}
+
         const requiredOptions = {
             env: {
                 ...process.env,
                 ...this._env,
                 ...originalSpawnOptions.env,
+                ...additionalEnvironmentVariables,
             },
         }
 
+        // TODO: Workaround for the bug fix here:
+        // https://github.com/neovim/neovim/pull/9345
+        // Once 0.3.2 is available and we've switched, we won't need this anymore.
+        if (Platform.isMac() && !requiredOptions.env.LANG) {
+            requiredOptions.env.LANG = "en_us.UTF-8"
+            Log.warn(
+                "'LANG' environment variable not set, using default value of 'en_us.UTF-8'. Consider setting environment.additionalVariables['LANG'].",
+            )
+        }
+
         requiredOptions.env.PATH = this.mergePathEnvironmentVariable(
             existingPath,
             configuration.getValue("environment.additionalPaths"),

browser/src/Services/Configuration/DefaultConfiguration.ts

@@ -176,6 +176,7 @@ const BaseConfiguration: IConfigurationValues = {
     "explorer.maxUndoFileSizeInBytes": 500_000,
 
     "environment.additionalPaths": [],
+    "environment.additionalVariables": {},
 
     "keyDisplayer.showInInsertMode": false,
 

browser/src/Services/Configuration/IConfigurationValues.ts

@@ -214,6 +214,9 @@ export interface IConfigurationValues {
     // (and available in terminal integration, later)
     "environment.additionalPaths": string[]
 
+    // Additional environment variables that override the default settings
+    "environment.additionalVariables": any
+
     // User configurable array of files for which
     // the image layer opens
     "editor.imageLayerExtensions": string[]