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

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

* snowpack/src/commands/install.ts (InstallRunResult): export it.

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

snowpack/src/commands/dev.ts

@@ -94,6 +94,8 @@ 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.`;
 
 /**
@@ -1320,8 +1322,16 @@ export async function startDevServer(commandOptions: CommandOptions): Promise<Sn
       .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()
+        .then(() => {
+          hmrEngine.broadcastMessage({type: 'reload'})
+          working = null;
+        });
   }
   const depWatcher = chokidar.watch([...symlinkedFileLocs], {
     cwd: '/', // we’re using absolute paths, so watch from root

snowpack/src/commands/install.ts

@@ -60,7 +60,7 @@ interface InstallRunOptions extends CommandOptions {
   shouldPrintStats: boolean;
 }
 
-interface InstallRunResult {
+export interface InstallRunResult {
   importMap: ImportMap;
   newLockfile: ImportMap | null;
   stats: DependencyStatsOutput | null;

snowpack/src/sources/local.ts

@@ -3,7 +3,7 @@ import {ImportMap} from 'esinstall';
 import {existsSync, promises as fs} from 'fs';
 import * as colors from 'kleur/colors';
 import path from 'path';
-import {getInstallTargets, run as installRunner} from '../commands/install';
+import {InstallRunResult, getInstallTargets, run as installRunner} from '../commands/install';
 import {logger} from '../logger';
 import {CommandOptions, PackageSource, SnowpackConfig} from '../types';
 import {checkLockfileHash, DEV_DEPENDENCIES_DIR, updateLockfileHash} from '../util';
@@ -13,12 +13,13 @@ import {checkLockfileHash, DEV_DEPENDENCIES_DIR, updateLockfileHash} from '../ut
  * 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(commandOptions: CommandOptions) {
+export async function installDependencies(commandOptions:CommandOptions = installCommandOptions)
+: Promise<InstallRunResult | null>{
   const {config} = commandOptions;
   const installTargets = await getInstallTargets(config);
   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({