feat(): do not complain on node_modules missing when beforeBuild is set

docs/configuration/configuration.md

@@ -114,7 +114,7 @@ Env file `electron-builder.env` in the current dir ([example](https://github.com
 ---
 
 * <code id="Configuration-afterSign">afterSign</code> (context: AfterPackContext) => Promise | null - The function (or path to file or module id) to be run after pack and sign (but before pack into distributable format).
-* <code id="Configuration-beforeBuild">beforeBuild</code> (context: BeforeBuildContext) => Promise | null - The function (or path to file or module id) to be run before dependencies are installed or rebuilt. Works when `npmRebuild` is set to `true`. Resolving to `false` will skip dependencies install or rebuild.
+* <code id="Configuration-beforeBuild">beforeBuild</code> (context: BeforeBuildContext) => Promise | null - The function (or path to file or module id) to be run before dependencies are installed or rebuilt. Works when `npmRebuild` is set to `true`. If provided and `node_modules` are missing it will not invoke production dependencies check. Resolving to `false` will skip dependencies install or rebuild.
 * <code id="Configuration-remoteBuild">remoteBuild</code> = `true` Boolean - Whether to build using Electron Build Service if target not supported on current OS.
 * <code id="Configuration-includePdb">includePdb</code> = `false` Boolean - Whether to include PDB files.
 * <code id="Configuration-removePackageScripts">removePackageScripts</code> = `true` Boolean - Whether to remove `scripts` field from `package.json` files.

packages/electron-builder-lib/src/packager.ts

@@ -3,7 +3,7 @@ import { deepAssign, addValue, Arch, archFromString, AsyncTaskManager, DebugLogg
 import { CancellationToken } from "builder-util-runtime"
 import { executeFinally, orNullIfFileNotExist } from "builder-util/out/promise"
 import { EventEmitter } from "events"
-import { ensureDir, outputFile } from "fs-extra-p"
+import { ensureDir, outputFile, existsSync } from "fs-extra-p"
 import isCI from "is-ci"
 import { dump } from "js-yaml"
 import { Lazy } from "lazy-val"
@@ -91,8 +91,13 @@ export class Packager {
   get productionDeps(): Lazy<Array<Dependency>> {
     let result = this._productionDeps
     if (result == null) {
-      result = createLazyProductionDeps(this.appDir)
-      this._productionDeps = result
+      if (!this.config.beforeBuild || existsSync(path.join(this.appDir, "node_modules"))) {
+        result = createLazyProductionDeps(this.appDir)
+        this._productionDeps = result
+      } else {
+        // https://github.com/electron-userland/electron-builder/issues/2551
+        return new Lazy(() => Promise.resolve([]))
+      }
     }
     return result
   }