Allow to exclude web architectures in development mode

This commit implements an --exclude-archs arg to the run command
which allows you to pass a comma-seperated list of architectures
to exclude.

Motivation:
Improve rebuild speeds, by allowing to leave out certain
web architectures during development.

Meteor rebuild speeds, although greatly improved in recent versions,
is still a common point of frustration as seen in the issues (meteor#10800)
and on the forum (https://forums.meteor.com/t/2x-to-3x-longer-build-time-also-on-testing-since-1-8-2-update/51028/3)

One reason for slow rebuilds is high memory pressure (meteor#9568).
The web.browser.legacy architecture is currently always being build
while most of us will only test this every once in a while.
So while we don't need it most of times during development
it does add to the high memory usage.
Furthermore, even though these builds are delayed,
long-running synchronous tasks have the potential to block the server startup (meteor#10261).
This last issue can be partially, but not fully, improved by meteor#10427
Therefore a commonly requested feature has been to disable the legacy build (meteor/meteor-feature-requests#333)

However, we may also temporarily disable cordova builds
and we may even want to disable just the web.browser build if we're just debugging
a bug in the legacy build.
Therefore I chose to create the more generic --exclude-archs option.

History.md

@@ -103,6 +103,13 @@ N/A
 
 * The `typescript` npm package has been updated to version 3.7.3.
 
+* You can now use the `--exclude-archs` CLI argument for the run and test 
+  commands to temporarily disable building certain web architectures.
+  For example: `meteor run --exclude-archs web.browser.legacy`.
+  You can pass multiple architectures comma seperated.
+  This can be used to improve rebuild times if you're not actively testing
+  those architectures during development.
+
 ## v1.8.2, 2019-11-14
 
 ### Breaking changes

packages/appcache/appcache-server.js

@@ -251,10 +251,12 @@ function eachResource({
 }
 
 function sizeCheck() {
-  const sizes = [ // Check size of each known architecture independently.
+  const RESOURCE_SIZE_LIMIT = 5 * 1024 * 1024; // 5MB
+  const largeSizes = [ // Check size of each known architecture independently.
     "web.browser",
     "web.browser.legacy",
-  ].reduce((filt, arch) => {
+  ].filter((arch) => !!WebApp.clientPrograms[arch])
+  .map((arch) => {
     let totalSize = 0;
 
     WebApp.clientPrograms[arch].manifest.forEach(resource => {
@@ -265,22 +267,21 @@ function sizeCheck() {
       }
     });
 
-    if (totalSize > 5 * 1024 * 1024) {
-      filt.push({
-        arch,
-        size: totalSize
-      });
+    return {
+      arch,
+      size: totalSize,
     }
-    return filt;
-  }, []);
-  if (sizes.length > 0) {
+  })
+  .filter(({ size }) => size > RESOURCE_SIZE_LIMIT);
+
+  if (largeSizes.length > 0) {
     Meteor._debug([
       "** You are using the appcache package, but the size of",
       "** one or more of your cached resources is larger than",
       "** the recommended maximum size of 5MB which may break",
       "** your app in some browsers!",
       "** ",
-      ...sizes.map(data => `** ${data.arch}: ${(data.size / 1024 / 1024).toFixed(1)}MB`),
+      ...largeSizes.map(data => `** ${data.arch}: ${(data.size / 1024 / 1024).toFixed(1)}MB`),
       "** ",
       "** See http://docs.meteor.com/#appcache for more",
       "** information and fixes."

packages/webapp/webapp_server.js

@@ -402,6 +402,12 @@ WebAppInternals.staticFilesMiddleware = async function (
     identifyBrowser(req.headers["user-agent"]),
   );
 
+  if (! hasOwn.call(WebApp.clientPrograms, arch)) {
+    // We could come here in case we run with some architectures excluded
+    next();
+    return;
+  }
+
   // If pauseClient(arch) has been called, program.paused will be a
   // Promise that will be resolved when the program is unpaused.
   const program = WebApp.clientPrograms[arch];
@@ -985,6 +991,19 @@ function runWebAppServer() {
         request.browser,
       );
 
+      if (! hasOwn.call(WebApp.clientPrograms, arch)) {
+        // We could come here in case we run with some architectures excluded
+        headers['Cache-Control'] = 'no-cache';
+        res.writeHead(404, headers);
+        if (Meteor.isDevelopment) {
+          res.end(`No client program found for the ${arch} architecture.`);
+        } else {
+          // Safety net, but this branch should not be possible.
+          res.end("404 Not Found");
+        }
+        return;
+      }
+
       // If pauseClient(arch) has been called, program.paused will be a
       // Promise that will be resolved when the program is unpaused.
       await WebApp.clientPrograms[arch].paused;

tools/cli/commands.js

@@ -162,6 +162,16 @@ export function parseRunTargets(targets) {
   });
 };
 
+const excludableWebArchs = ['web.browser', 'web.browser.legacy', 'web.cordova'];
+function filterWebArchs(webArchs, excludeArchsOption) {
+  if (excludeArchsOption) {
+    const excludeArchs = excludeArchsOption.trim().split(/\s*,\s*/)
+      .filter(arch => excludableWebArchs.includes(arch));
+    webArchs = webArchs.filter(arch => !excludeArchs.includes(arch));
+  }
+  return webArchs;
+}
+
 ///////////////////////////////////////////////////////////////////////////////
 // options that act like commands
 ///////////////////////////////////////////////////////////////////////////////
@@ -318,7 +328,8 @@ var runCommandOptions = {
     // Allow the version solver to make breaking changes to the versions
     // of top-level dependencies.
     'allow-incompatible-update': { type: Boolean },
-    'extra-packages': { type: String }
+    'extra-packages': { type: String },
+    'exclude-archs': { type: String }
   },
   catalogRefresh: new catalog.Refresh.Never()
 };
@@ -399,6 +410,7 @@ function doRunCommand(options) {
       webArchs.push("web.cordova");
     }
   }
+  webArchs = filterWebArchs(webArchs, options['exclude-archs']);
 
   let cordovaRunner;
   if (!_.isEmpty(runTargets)) {
@@ -1635,7 +1647,9 @@ testCommandOptions = {
     // For 'test-packages': Run in "full app" mode
     'full-app': { type: Boolean, 'default': false },
 
-    'extra-packages': { type: String }
+    'extra-packages': { type: String },
+
+    'exclude-archs': { type: String }
   }
 };
 
@@ -1978,6 +1992,11 @@ var runTestAppForPackages = function (projectContext, options) {
     minifyMode: options.production ? 'production' : 'development'
   };
   buildOptions.buildMode = "test";
+  let webArchs = projectContext.platformList.getWebArchs();
+  if (options.cordovaRunner) {
+    webArchs.push("web.cordova");
+  }
+  buildOptions.webArchs = filterWebArchs(webArchs, options['exclude-archs']);
 
   if (options.deploy) {
     // Run the constraint solver and build local packages.

tools/cli/help.txt

@@ -103,6 +103,9 @@ Options:
                    version constraints.
   --extra-packages Run with additional packages (comma separated, for example:
                    --extra-packages "package-name1, [email protected]")
+  --exclude-archs  Don't create bundles for certain web architectures
+                  (comma separated, for example:
+                   --exclude-archs "web.browser.legacy, web.cordova")
 
 >>> debug
 Run the project with server-side debugging enabled.
@@ -713,6 +716,9 @@ Options:
   --driver-package  Name of the optional test driver package to use to run
                     tests and display results. For example:
                     --driver-package practicalmeteor:mocha
+  --exclude-archs   Don't create test bundles for certain web architectures
+                    (comma separated, for example:
+                    --exclude-archs "web.browser.legacy, web.cordova")
 
 >>> self-test
 Run tests of the 'meteor' tool.