add manual watching plugin

Author: lobsterkatie

packages/browser/rollup.npm.config.js

@@ -4,5 +4,6 @@ export default makeNPMConfigVariants(
   makeBaseNPMConfig({
     // packages with bundles have a different build directory structure
     hasBundles: true,
+    watchPackages: ['core'],
   }),
 );

packages/core/rollup.npm.config.js

@@ -1,3 +1,7 @@
 import { makeBaseNPMConfig, makeNPMConfigVariants } from '../../rollup/index.js';
 
-export default makeNPMConfigVariants(makeBaseNPMConfig());
+export default makeNPMConfigVariants(
+  makeBaseNPMConfig({
+    watchPackages: ['hub'],
+  }),
+);

packages/gatsby/rollup.npm.config.js

@@ -1,3 +1,7 @@
 import { makeBaseNPMConfig, makeNPMConfigVariants } from '../../rollup/index.js';
 
-export default makeNPMConfigVariants(makeBaseNPMConfig());
+export default makeNPMConfigVariants(
+  makeBaseNPMConfig({
+    watchPackages: ['react', 'tracing'],
+  }),
+);

packages/hub/rollup.npm.config.js

@@ -1,3 +1,7 @@
 import { makeBaseNPMConfig, makeNPMConfigVariants } from '../../rollup/index.js';
 
-export default makeNPMConfigVariants(makeBaseNPMConfig());
+export default makeNPMConfigVariants(
+  makeBaseNPMConfig({
+    watchPackages: ['utils'],
+  }),
+);

packages/integrations/rollup.npm.config.js

@@ -4,5 +4,6 @@ export default makeNPMConfigVariants(
   makeBaseNPMConfig({
     // packages with bundles have a different build directory structure
     hasBundles: true,
+    watchPackages: ['utils'],
   }),
 );

packages/nextjs/rollup.npm.config.js

@@ -8,5 +8,6 @@ export default makeNPMConfigVariants(
     // prevent this nextjs code from ending up in our built package (this doesn't happen automatially because the name
     // doesn't match an SDK dependency)
     externals: ['next/router'],
+    watchPackages: ['integrations', 'node', 'react', 'tracing'],
   }),
 );

packages/node/rollup.npm.config.js

@@ -1,3 +1,7 @@
 import { makeBaseNPMConfig, makeNPMConfigVariants } from '../../rollup/index.js';
 
-export default makeNPMConfigVariants(makeBaseNPMConfig());
+export default makeNPMConfigVariants(
+  makeBaseNPMConfig({
+    watchPackages: ['core'],
+  }),
+);

packages/react/rollup.npm.config.js

@@ -3,5 +3,6 @@ import { makeBaseNPMConfig, makeNPMConfigVariants } from '../../rollup/index.js'
 export default makeNPMConfigVariants(
   makeBaseNPMConfig({
     esModuleInterop: true,
+    watchPackages: ['browser'],
   }),
 );

packages/serverless/rollup.npm.config.js

@@ -3,5 +3,6 @@ import { makeBaseNPMConfig, makeNPMConfigVariants } from '../../rollup/index.js'
 export default makeNPMConfigVariants(
   makeBaseNPMConfig({
     entrypoints: ['src/index.ts', 'src/awslambda-auto.ts'],
+    watchPackages: ['node', 'tracing'],
   }),
 );

packages/tracing/rollup.npm.config.js

@@ -4,5 +4,6 @@ export default makeNPMConfigVariants(
   makeBaseNPMConfig({
     // packages with bundles have a different build directory structure
     hasBundles: true,
+    watchPackages: ['browser'],
   }),
 );

packages/utils/rollup.npm.config.js

@@ -5,5 +5,6 @@ export default makeNPMConfigVariants(
     // We build the polyfills separately because they're not included in the top-level exports of the package, in order
     // to keep them out of the public API.
     entrypoints: ['src/index.ts', 'src/buildPolyfills/index.ts'],
+    watchPackages: ['types'],
   }),
 );

packages/vue/rollup.npm.config.js

@@ -1,3 +1,7 @@
 import { makeBaseNPMConfig, makeNPMConfigVariants } from '../../rollup/index.js';
 
-export default makeNPMConfigVariants(makeBaseNPMConfig());
+export default makeNPMConfigVariants(
+  makeBaseNPMConfig({
+    watchPackages: ['browser'],
+  }),
+);

packages/wasm/rollup.npm.config.js

@@ -4,5 +4,6 @@ export default makeNPMConfigVariants(
   makeBaseNPMConfig({
     // packages with bundles have a different build directory structure
     hasBundles: true,
+    watchPackages: ['browser'],
   }),
 );

rollup/npmHelpers.js

@@ -14,6 +14,7 @@ import {
   makeRemoveBlankLinesPlugin,
   makeRemoveESLintCommentsPlugin,
   makeSucrasePlugin,
+  makeWatchDependenciesPlugin,
 } from './plugins/index.js';
 
 const packageDotJSON = require(path.resolve(process.cwd(), './package.json'));
@@ -24,8 +25,10 @@ export function makeBaseNPMConfig(options = {}) {
     esModuleInterop = false,
     externals: packageSpecificExternals = [],
     hasBundles = false,
+    watchPackages = [],
   } = options;
 
+  const watchDependenciesPlugin = makeWatchDependenciesPlugin(watchPackages);
   const nodeResolvePlugin = makeNodeResolvePlugin();
   const sucrasePlugin = makeSucrasePlugin();
   const constToVarPlugin = makeConstToVarPlugin();
@@ -77,6 +80,7 @@ export function makeBaseNPMConfig(options = {}) {
     },
 
     plugins: [
+      watchDependenciesPlugin,
       nodeResolvePlugin,
       sucrasePlugin,
       constToVarPlugin,

rollup/plugins/npmPlugins.js

@@ -4,6 +4,8 @@
  * Sucrase plugin docs: https://github.com/rollup/plugins/tree/master/packages/sucrase
  */
 
+import * as path from 'path';
+
 // We need both replacement plugins because one handles regex and the other runs both before and after rollup does its
 // bundling work.
 import regexReplace from 'rollup-plugin-re';
@@ -98,4 +100,38 @@ export function makeRemoveBlankLinesPlugin() {
   });
 }
 
+/**
+ * Create a plugin to manually add packages to a build's watch.
+ *
+ * Unlike tsc, rollup doesn't seem to be able to follow the symlinks that yarn workspaces uses to link our packages into
+ * one another, with the result that changes don't automatically cascade in watch mode. This plugin sets that up
+ * manually.
+ *
+ * TODO: This currently only works when running `build:watch` or `build:dev:watch` at the repo level, not the individual
+ * package level.
+ *
+ * TODO: At the moment, in the interests (current) time and (future) build spped, the watch list for each package is
+ * hardcoded into its rollup config. While the values in those lists are likely to be highly stable over time, there's
+ * also no mechanism to guarantee that changes in a package's intra-package dependencies will be reflected in the lists.
+ * It shouldn't be that hard to write a script to generate the correct lists at build time, though, and hopefully it
+ * wouldn't add a ton of time to the build. (It'd be a lot of file IO reading all of the `package.json` files, but
+ * computers are also fast. We'd have to experiement.)
+ *
+ * @param watchPackages The packages to watch. Shouldn't include any transitive dependencies, even if they're also
+ * direct dependencies. (In other words, if A depends on B and C, and B depends on C, then A should only list B, not C.)
+ *
+ * @returns A plugin which will add the given packages to a build's watch list if the build is running in watch mode.
+ */
+export function makeWatchDependenciesPlugin(watchPackages) {
+  return {
+    name: 'watch-dependencies',
+    buildStart: function () {
+      if (this.meta.watchMode) {
+        const cwd = process.cwd();
+        watchPackages.forEach(pkg => this.addWatchFile(path.resolve(cwd, `../${pkg}`)));
+      }
+    },
+  };
+}
+
 export { makeExtractPolyfillsPlugin } from './extractPolyfillsPlugin.js';