add script to remove empty imports/requires (#735)

* add script to remove empty imports/requires

* add changeset

* remove the minified entries because of CI

.changeset/strong-radios-judge.md

@@ -0,0 +1,5 @@
+---
+'@urql/core': patch
+---
+
+Add a babel-plugin that removes empty imports from the final build output.

packages/core/package.json

@@ -48,6 +48,7 @@
     "check": "tsc --noEmit",
     "lint": "eslint --ext=js,jsx,ts,tsx .",
     "build": "rollup -c ../../scripts/rollup/config.js",
+    "postbuild": "node ./scripts/remove-empty-imports.js",
     "prepare": "../../scripts/prepare/index.js",
     "prepublishOnly": "run-s clean build"
   },

packages/core/scripts/remove-empty-imports.js

@@ -0,0 +1,38 @@
+const { transformSync: transform } = require('@babel/core');
+const fs = require('fs');
+
+const nonMinified = [
+  `${process.cwd()}/dist/urql-core.js`,
+  `${process.cwd()}/dist/urql-core.mjs`,
+  `${process.cwd()}/dist/urql-core-internal.js`,
+  `${process.cwd()}/dist/urql-core-internal.mjs`,
+];
+
+const removeEmptyImports = (babel) => {
+  const { types: t } = babel;
+
+  return {
+    visitor: {
+      ImportDeclaration(path) {
+        const { specifiers } = path.node
+        if (specifiers.length === 0) {
+          path.remove();
+        }
+      },
+      CallExpression(path) {
+        if (
+          t.isIdentifier(path.node.callee) &&
+          path.node.callee.name === 'require' &&
+          path.parent.type !== 'VariableDeclarator'
+        ) {
+          path.remove();
+        }
+      }
+    }
+  };
+}
+
+nonMinified.forEach(loc => {
+  const { code: newCode } = transform(fs.readFileSync(loc), { plugins: [removeEmptyImports], babelrc: false });
+  fs.writeFileSync(loc, newCode);
+});