Cleaner promise pattern

Author: plemarquand

src/SwiftPackage.ts

@@ -23,7 +23,7 @@ import { BuildFlags } from "./toolchain/BuildFlags";
 import { SwiftToolchain } from "./toolchain/toolchain";
 import { isPathInsidePath } from "./utilities/filesystem";
 import { lineBreakRegex } from "./utilities/tasks";
-import { execSwift, getErrorDescription, hashString } from "./utilities/utilities";
+import { execSwift, getErrorDescription, hashString, unwrapPromise } from "./utilities/utilities";
 
 /** Swift Package Manager contents */
 export interface PackageContents {
@@ -199,7 +199,6 @@ export class SwiftPackage {
     private _contents: SwiftPackageState | undefined;
     private contentsPromise: Promise<SwiftPackageState>;
     private contentsResolve: (value: SwiftPackageState | PromiseLike<SwiftPackageState>) => void;
-    private contentsReject: (reason?: unknown) => void;
 
     /**
      * SwiftPackage Constructor
@@ -213,14 +212,9 @@ export class SwiftPackage {
         // TODO: Make private again
         public workspaceState: WorkspaceState | undefined
     ) {
-        let res: (value: SwiftPackageState | PromiseLike<SwiftPackageState>) => void;
-        let rej: (reason?: unknown) => void;
-        this.contentsPromise = new Promise((resolve, reject) => {
-            res = resolve;
-            rej = reject;
-        });
-        this.contentsResolve = res!;
-        this.contentsReject = rej!;
+        const { promise, resolve } = unwrapPromise<SwiftPackageState>();
+        this.contentsPromise = promise;
+        this.contentsResolve = resolve;
     }
 
     /**
@@ -381,14 +375,10 @@ export class SwiftPackage {
 
     /** Reload swift package */
     public async reload(folderContext: FolderContext, disableSwiftPMIntegration: boolean = false) {
-        let res: (value: SwiftPackageState | PromiseLike<SwiftPackageState>) => void;
-        let rej: (reason?: unknown) => void;
-        this.contentsPromise = new Promise((resolve, reject) => {
-            res = resolve;
-            rej = reject;
-        });
-        this.contentsResolve = res!;
-        this.contentsReject = rej!;
+        const { promise, resolve } = unwrapPromise<SwiftPackageState>();
+        this.contentsPromise = promise;
+        this.contentsResolve = resolve;
+
         const loadedContents = await this.loadPackageState(
             folderContext,
             disableSwiftPMIntegration

src/utilities/utilities.ts

@@ -315,6 +315,21 @@ export function compactMap<T, U>(
         return acc;
     }, []);
 }
+
+/**
+ * Create a promise that can be resolved outside the promise executor.
+ * @returns An object containing the promise that can be awaited, and its resolve and reject functions.
+ */
+export function unwrapPromise<T>() {
+    let resolve: (value: T | PromiseLike<T>) => void;
+    let reject: (reason?: unknown) => void;
+    const promise = new Promise<T>((res, rej) => {
+        resolve = res;
+        reject = rej;
+    });
+    return { promise, resolve: resolve!, reject: reject! };
+}
+
 /**
  * Get path to swift executable, or executable in swift bin folder
  *