Wire up the @apollo/client/cache entry point

Similar to the changes made in #5541, this commit adds a direct
entry point for the Apollo Client cache code. Importing from
`@apollo/client/cache` gives access to the cache code directly,
without pulling in other parts of the Apollo Client codebase.

config/prepareDist.js

@@ -14,6 +14,8 @@
 const fs = require('fs');
 const recast = require('recast');
 
+const distRoot = `${__dirname}/../dist`;
+
 
 /* @apollo/client */
 
@@ -42,7 +44,7 @@ const distPackageJson = JSON.stringify(packageJson, (_key, value) => {
 }, 2) + "\n";
 
 // Save the modified package.json to "dist"
-fs.writeFileSync(`${__dirname}/../dist/package.json`, distPackageJson);
+fs.writeFileSync(`${distRoot}/package.json`, distPackageJson);
 
 // Copy supporting files into "dist"
 const srcDir = `${__dirname}/..`;
@@ -51,7 +53,7 @@ fs.copyFileSync(`${srcDir}/README.md`,  `${destDir}/README.md`);
 fs.copyFileSync(`${srcDir}/LICENSE`,  `${destDir}/LICENSE`);
 
 
-/* @apollo/client/core */
+/* @apollo/client/core, @apollo/client/cache */
 
 function buildPackageJson(bundleName) {
   return JSON.stringify({
@@ -62,33 +64,42 @@ function buildPackageJson(bundleName) {
   }, null, 2) + "\n";
 }
 
-// Create a `core` bundle package.json, storing it in the dist core
-// directory. This helps provide a way for Apollo Client to be used without
-// React, via `@apollo/client/core`.
-fs.writeFileSync(
-  `${__dirname}/../dist/core/package.json`,
-  buildPackageJson('core')
-);
-
-// Build a new `core.cjs.js` entry point file, that includes everything
-// except the exports listed in `src/react/index.ts`. Copy this file into
-// the `dist/core` directory, to allow Apollo Client core only imports
-// using `@apollo/client/core`.
-
-const reactIndexSrc = fs.readFileSync(`${__dirname}/../dist/react/index.js`);
-const reactExports = [];
-recast.visit(recast.parse(reactIndexSrc), {
-  visitExportSpecifier(path) {
-    reactExports.push(path.value.exported.name);
-    return false;
-  },
-});
-
-fs.writeFileSync(`${__dirname}/../dist/core/core.cjs.js`, [
-  "const allExports = require('../apollo-client.cjs');",
-  `const reactExportNames = new Set(${JSON.stringify(reactExports)});`,
-  "Object.keys(allExports).forEach(name => {",
-  "  if (!reactExportNames.has(name)) exports[name] = allExports[name];",
-  "});",
-  "",
-].join('\n'));
+function loadExportNames(bundleName) {
+  const indexSrc =
+    fs.readFileSync(`${distRoot}/${bundleName}/index.js`);
+  const exportNames = [];
+  recast.visit(recast.parse(indexSrc), {
+    visitExportSpecifier(path) {
+      exportNames.push(path.value.exported.name);
+      return false;
+    },
+  });
+  return exportNames;
+}
+
+function writeCjsIndex(bundleName, exportNames, includeNames = true) {
+  const filterPrefix = includeNames ? '' : '!';
+  fs.writeFileSync(`${distRoot}/${bundleName}/${bundleName}.cjs.js`, [
+    "const allExports = require('../apollo-client.cjs');",
+    `const names = new Set(${JSON.stringify(exportNames)});`,
+    "Object.keys(allExports).forEach(name => {",
+    `  if (${filterPrefix}names.has(name)) {`,
+    "    exports[name] = allExports[name];",
+    "  }",
+    "});",
+    "",
+  ].join('\n'));
+}
+
+// Create `core` and `cache` bundle package.json files, storing them in their
+// associated dist directory. This helps provide a way for the Apollo Client
+// core to be used without React (via `@apollo/client/core`), and the cache
+// to be used by itself (via `@apollo/client/cache`). Also create
+// `core.cjs.js` and `cache.cjs.js` CommonJS entry point files that only
+// include the exports needed for each bundle.
+
+fs.writeFileSync(`${distRoot}/core/package.json`, buildPackageJson('core'));
+writeCjsIndex('core', loadExportNames('react'), false);
+
+fs.writeFileSync(`${distRoot}/cache/package.json`, buildPackageJson('cache'));
+writeCjsIndex('cache', loadExportNames('cache'));

src/cache/index.ts

@@ -0,0 +1,10 @@
+export { Transaction, ApolloCache } from './core/cache';
+export { Cache } from './core/types/Cache';
+export { DataProxy } from './core/types/DataProxy';
+
+export {
+  InMemoryCache,
+  InMemoryCacheConfig,
+} from './inmemory/inMemoryCache';
+export { defaultDataIdFromObject } from './inmemory/policies';
+export * from './inmemory/types';

src/core/index.ts

@@ -34,15 +34,7 @@ export { isApolloError, ApolloError } from '../errors/ApolloError';
 
 /* Cache */
 
-export { Transaction, ApolloCache } from '../cache/core/cache';
-export { Cache } from '../cache/core/types/Cache';
-export { DataProxy } from '../cache/core/types/DataProxy';
-export {
-  InMemoryCache,
-  InMemoryCacheConfig,
-} from '../cache/inmemory/inMemoryCache';
-export { defaultDataIdFromObject } from '../cache/inmemory/policies';
-export * from '../cache/inmemory/types';
+export * from '../cache';
 
 /* Link */