Fix #2088: unbreak automatic reinstall of linked dependencies on change

* snowpack/src/commands/dev.ts (installDependencies): import it.
(onDepWatchEvent): Call it.

* snowpack/src/sources/local-install.ts (InstallRunResult): export it.

* snowpack/src/sources/local.ts (InstallRunResult): import it.
(installDependencies): export it and give it a type.

snowpack/src/commands/dev.ts

@@ -96,6 +96,8 @@ interface FoundFile {
   isResolve: boolean;
 }
 
+import {installDependencies} from '../sources/local';
+
 const FILE_BUILD_RESULT_ERROR = `Build Result Error: There was a problem with a file build result.`;
 
 /**
@@ -1341,8 +1343,16 @@ export async function startServer(commandOptions: CommandOptions): Promise<Snowp
       .filter(([_, packageManifest]) => packageManifest && !packageManifest['_id']) // only watch symlinked deps for now
       .map(([fileLoc]) => `${path.dirname(fileLoc!)}/**`),
   );
+
+  let working : Promise<any> | null = null; // only one installl at a time
   function onDepWatchEvent() {
-    hmrEngine.broadcastMessage({type: 'reload'});
+    if (!working)
+      // FIXME: If one changes, reinstall _all_.  Inefficient?
+      working = installDependencies(config)
+        .then(() => {
+          hmrEngine.broadcastMessage({type: 'reload'})
+          working = null;
+        });
   }
   const depWatcher = chokidar.watch([...symlinkedFileLocs], {
     cwd: '/', // we’re using absolute paths, so watch from root

snowpack/src/sources/local-install.ts

@@ -18,7 +18,7 @@ interface InstallRunOptions {
   shouldPrintStats: boolean;
 }
 
-interface InstallRunResult {
+export interface InstallRunResult {
   importMap: ImportMap;
   newLockfile: ImportMap | null;
   stats: DependencyStatsOutput | null;

snowpack/src/sources/local.ts

@@ -6,7 +6,7 @@ import {ImportMap, InstallOptions as EsinstallOptions} from 'esinstall';
 import {existsSync, promises as fs} from 'fs';
 import * as colors from 'kleur/colors';
 import path from 'path';
-import {run as installRunner} from './local-install';
+import {InstallRunResult, run as installRunner} from './local-install';
 import {logger} from '../logger';
 import {getInstallTargets} from '../scan-imports';
 import {CommandOptions, PackageSource, PackageSourceLocal, SnowpackConfig} from '../types';
@@ -26,14 +26,15 @@ const DEV_DEPENDENCIES_DIR = path.join(PROJECT_CACHE_DIR, process.env.NODE_ENV |
  * your entire source app for dependency install targets, installs them,
  * and then updates the "hash" file used to check node_modules freshness.
  */
-async function installDependencies(config: SnowpackConfig) {
+export async function installDependencies(config: SnowpackConfig)
+: Promise <InstallRunResult | null> {
   const installTargets = await getInstallTargets(
     config,
     config.packageOptions.source === 'local' ? config.packageOptions.knownEntrypoints : [],
   );
   if (installTargets.length === 0) {
     logger.info('Nothing to install.');
-    return;
+    return null;
   }
   // 2. Install dependencies, based on the scan of your final build.
   const installResult = await installRunner({