Import lazy* from api repo (#1159)

CHANGELOG.md

@@ -5,6 +5,7 @@
 Changes:
 
 - Add `objectClear` and `objectSpread` utility functions
+- Add `lazyMethod` & `lazyMethods` utility functions
 - Sync with upstream Substrate ss58 registry
 
 

package.json

@@ -29,7 +29,7 @@
   },
   "devDependencies": {
     "@babel/core": "^7.16.0",
-    "@polkadot/dev": "^0.63.23",
+    "@polkadot/dev": "^0.63.24",
     "@polkadot/ts": "^0.4.13",
     "@types/ed2curve": "^0.2.2",
     "@types/jest": "^27.0.2"

packages/util/src/bundle.ts

@@ -15,6 +15,7 @@ export * from './extractTime';
 export * from './format';
 export * from './hex';
 export * from './is';
+export * from './lazy';
 export * from './logger';
 export * from './memoize';
 export * from './number';

packages/util/src/lazy.ts

@@ -0,0 +1,55 @@
+// Copyright 2017-2021 @polkadot/types authors & contributors
+// SPDX-License-Identifier: Apache-2.0
+
+import { isUndefined } from './is/undefined';
+
+type AnyFn = (...args: unknown[]) => unknown;
+
+type WithToString = { toString: () => string };
+
+export function lazyMethod <T, K> (result: Record<string, T> | AnyFn, item: K, creator: (d: K) => T, getName?: (d: K) => string): void {
+  const name = getName
+    ? getName(item)
+    : (item as WithToString).toString();
+  let value: T | undefined;
+
+  Object.defineProperty(result, name, {
+    // This allows for re-configuration with the embedded defineProperty below
+    // and ensures that on tested browsers and Node, it _will_ be redefined
+    // and thus short-circuited for future access
+    configurable: true,
+    enumerable: true,
+
+    // Use a function here, we don't want to capture the outer this, i.e.
+    // don't use arrow functions in this context since we have a this inside
+    get: function (): T {
+      // This check should _always_ be false and unneeded, since we override
+      // with a value below ... however we ensure we are quire vigilant against
+      // all environment failures, so we are rather be safe than sorry
+      if (isUndefined(value)) {
+        value = creator(item);
+
+        try {
+          // re-define the property as a value, next time around this
+          // getter will only return the computed value
+          Object.defineProperty(this, name, { value });
+        } catch {
+          // ignore any errors, since this _should_ not happen due to
+          // the "configurable" property above. But if it ever does
+          // from here-on we will be the cached value the next time
+          // around (with a very slight dip in performance)
+        }
+      }
+
+      return value;
+    }
+  });
+}
+
+export function lazyMethods <T, K> (result: Record<string, T>, items: K[], creator: (v: K) => T, getName?: (m: K) => string): Record<string, T> {
+  for (let i = 0; i < items.length; i++) {
+    lazyMethod(result, items[i], creator, getName);
+  }
+
+  return result;
+}

yarn.lock

@@ -1930,9 +1930,9 @@ __metadata:
   languageName: node
   linkType: hard
 
-"@polkadot/dev@npm:^0.63.23":
-  version: 0.63.23
-  resolution: "@polkadot/dev@npm:0.63.23"
+"@polkadot/dev@npm:^0.63.24":
+  version: 0.63.24
+  resolution: "@polkadot/dev@npm:0.63.24"
   dependencies:
     "@babel/cli": ^7.16.0
     "@babel/core": ^7.16.0
@@ -2017,7 +2017,7 @@ __metadata:
     polkadot-exec-rollup: scripts/polkadot-exec-rollup.mjs
     polkadot-exec-tsc: scripts/polkadot-exec-tsc.mjs
     polkadot-exec-webpack: scripts/polkadot-exec-webpack.mjs
-  checksum: f7c389cea148c32211e3ade061660d98294a017a73b7be0ebd50f1de86e7552f305af6eae36f49ee4df54f587d1638c68260e8c69a638fb5a889100b1ea47938
+  checksum: fd538da898f7c88dd5e3c939927af4726f75190b39aa299ab2481776eb6569356a7be8da9b32af294cd2d2083ae168c95faf69a207b0c82a0d2e6b282b434630
   languageName: node
   linkType: hard
 
@@ -9192,7 +9192,7 @@ resolve@^2.0.0-next.3:
   resolution: "root-workspace-0b6124@workspace:."
   dependencies:
     "@babel/core": ^7.16.0
-    "@polkadot/dev": ^0.63.23
+    "@polkadot/dev": ^0.63.24
     "@polkadot/ts": ^0.4.13
     "@types/ed2curve": ^0.2.2
     "@types/jest": ^27.0.2