fix(core): always call callback in DefaultStream._flush (#2255)

.yarn/versions/19147bf1.yml

@@ -0,0 +1,30 @@
+releases:
+  "@yarnpkg/core": patch
+  "@yarnpkg/plugin-workspace-tools": patch
+
+declined:
+  - "@yarnpkg/plugin-compat"
+  - "@yarnpkg/plugin-constraints"
+  - "@yarnpkg/plugin-dlx"
+  - "@yarnpkg/plugin-essentials"
+  - "@yarnpkg/plugin-exec"
+  - "@yarnpkg/plugin-file"
+  - "@yarnpkg/plugin-git"
+  - "@yarnpkg/plugin-github"
+  - "@yarnpkg/plugin-http"
+  - "@yarnpkg/plugin-init"
+  - "@yarnpkg/plugin-interactive-tools"
+  - "@yarnpkg/plugin-link"
+  - "@yarnpkg/plugin-node-modules"
+  - "@yarnpkg/plugin-npm"
+  - "@yarnpkg/plugin-npm-cli"
+  - "@yarnpkg/plugin-pack"
+  - "@yarnpkg/plugin-patch"
+  - "@yarnpkg/plugin-pnp"
+  - "@yarnpkg/plugin-stage"
+  - "@yarnpkg/plugin-typescript"
+  - "@yarnpkg/plugin-version"
+  - "@yarnpkg/builder"
+  - "@yarnpkg/cli"
+  - "@yarnpkg/doctor"
+  - "@yarnpkg/pnpify"

packages/yarnpkg-core/sources/miscUtils.ts

@@ -225,6 +225,8 @@ export class DefaultStream extends Transform {
   _flush(cb: any) {
     if (this.active && this.ifEmpty.length > 0) {
       cb(null, this.ifEmpty);
+    } else {
+      cb(null);
     }
   }
 }