Export lazy objects creation and modules import functionality to plugins

package.json

@@ -80,6 +80,7 @@
     "find-up": "^2.1.0",
     "fs-extra": "^7.0.1",
     "glob": "^7.1.3",
+    "import-lazy": "^3.1.0",
     "lodash": "^4.17.11",
     "mocha": "^5.1.1",
     "semver": "^5.6.0",

src/internal/util/lazy.ts

@@ -1,3 +1,5 @@
+import { Eth } from "web3x/eth";
+
 import { BuidlerError, ERRORS } from "../core/errors";
 
 export function lazyObject<T extends object>(objectCreator: () => T): T {
@@ -81,3 +83,45 @@ export function lazyObject<T extends object>(objectCreator: () => T): T {
     }
   });
 }
+
+/**
+ * This function is a lazy version of `require`. It imports a module
+ * synchronously, by creating a proxy that delays the actual `require` until
+ * the module is used.
+ *
+ * The disadvantage of using this technique is that the type information is
+ * lost. If done with enough care, this can be manually fixed.
+ *
+ * TypeScript doesn't emit `require` calls for modules that are imported only
+ * because of their types. So if one uses lazyImport along with a normal ESM
+ * import you can pass the module's type to this function.
+ *
+ * An example of this can be:
+ *
+ *   `import func from "func-mod";`
+ *   `const f = lazyImport<typeof func>("func-mod");`
+ *
+ * You can also pass it a selector to import just an element of the module:
+ *
+ *   `import { Eth } from "web3x/eth";`
+ *   `const LazyEth = lazyImport<Eth>("web3x/eth", "Eth");`
+ *
+ * Limitations:
+ *  - It's not entirely clear when to use `typeof`.
+ *  - If you get a compilation error saying something about "namespace" consider
+ *    using a selector.
+ */
+export function lazyImport<ModuleT = any>(
+  packageName: string,
+  selector?: string
+): ModuleT {
+  const importLazy = require("import-lazy");
+  const lazyRequire = importLazy(require);
+  const lazyModule = lazyRequire(packageName);
+
+  if (selector === undefined) {
+    return lazyModule;
+  }
+
+  return lazyObject(() => lazyModule[selector]);
+}

src/plugins.ts

@@ -4,3 +4,4 @@ export {
   readArtifact,
   readArtifactSync
 } from "./internal/artifacts";
+export { lazyObject, lazyImport } from "./internal/util/lazy";

yarn.lock

@@ -1772,6 +1772,11 @@ ieee754@^1.1.4:
   resolved "https://registry.yarnpkg.com/ieee754/-/ieee754-1.1.12.tgz#50bf24e5b9c8bb98af4964c941cdb0918da7b60b"
   integrity sha512-GguP+DRY+pJ3soyIiGPTvdiVXjZ+DbXOxGpXn3eMvNW4x4irjqXm4wHKscC+TfxSJ0yw/S1F24tqdMNsMZTiLA==
 
+import-lazy@^3.1.0:
+  version "3.1.0"
+  resolved "https://registry.yarnpkg.com/import-lazy/-/import-lazy-3.1.0.tgz#891279202c8a2280fdbd6674dbd8da1a1dfc67cc"
+  integrity sha512-8/gvXvX2JMn0F+CDlSC4l6kOmVaLOO3XLkksI7CI3Ud95KDYJuYur2b9P/PUt/i/pDAMd/DulQsNbbbmRRsDIQ==
+
 imurmurhash@^0.1.4:
   version "0.1.4"
   resolved "https://registry.yarnpkg.com/imurmurhash/-/imurmurhash-0.1.4.tgz#9218b9b2b928a238b13dc4fb6b6d576f231453ea"