fix(core): Ignore empty bin value in Manifest#load (#5743)

**What's the problem this PR addresses?**

Some packages pass an invalid empty string for a `bin` entry in their
`package.json`, for example
[[email protected]](https://github.com/webpack-contrib/mini-css-extract-plugin/blob/v0.4.5/package.json#L10)

The NodeModules linker already ignores empty entries:

https://github.com/yarnpkg/berry/blob/master/packages/plugin-nm/sources/NodeModulesLinker.ts#L982

However `scriptUtils` was not, and would append `""` to the bin path
(resulting in the directory itself, not a binary)

Resolves #5669 

**How did you fix it?**

Instead of trying to fix this everywhere that might use a manifest
`.bin` property, I just remove these entries from the manifest when it
is being loaded, since an empty `bin` does not seem to be a valid entry.
The npm docs for `package.json` make no mention of any special case for
when `bin` is set to an empty string.

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Author: rally25rs

.yarn/versions/fe7910e2.yml

@@ -0,0 +1,34 @@
+releases:
+  "@yarnpkg/cli": patch
+  "@yarnpkg/core": 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-nm"
+  - "@yarnpkg/plugin-npm"
+  - "@yarnpkg/plugin-npm-cli"
+  - "@yarnpkg/plugin-pack"
+  - "@yarnpkg/plugin-patch"
+  - "@yarnpkg/plugin-pnp"
+  - "@yarnpkg/plugin-pnpm"
+  - "@yarnpkg/plugin-stage"
+  - "@yarnpkg/plugin-typescript"
+  - "@yarnpkg/plugin-version"
+  - "@yarnpkg/plugin-workspace-tools"
+  - "@yarnpkg/builder"
+  - "@yarnpkg/doctor"
+  - "@yarnpkg/extensions"
+  - "@yarnpkg/nm"
+  - "@yarnpkg/pnpify"
+  - "@yarnpkg/sdks"

packages/yarnpkg-core/sources/Manifest.ts

@@ -278,14 +278,16 @@ export class Manifest {
 
     this.bin = new Map();
     if (typeof data.bin === `string`) {
-      if (this.name !== null) {
+      if (data.bin.trim() === ``) {
+        errors.push(new Error(`Invalid bin field`));
+      } else if (this.name !== null) {
         this.bin.set(this.name.name, normalizeSlashes(data.bin));
       } else {
         errors.push(new Error(`String bin field, but no attached package name`));
       }
     } else if (typeof data.bin === `object` && data.bin !== null) {
       for (const [key, value] of Object.entries(data.bin)) {
-        if (typeof value !== `string`) {
+        if (typeof value !== `string` || value.trim() === ``) {
           errors.push(new Error(`Invalid bin definition for '${key}'`));
           continue;
         }

packages/yarnpkg-core/tests/Manifest.test.ts

@@ -34,5 +34,25 @@ describe(`Manifest`, () => {
         [`start`, `node index.js`],
       ]);
     });
+
+    it(`should preserve bin if a string was specified`, () => {
+      const manifest = Manifest.fromText(`{ "name": "name", "bin": "./bin.js" }`);
+      expect(manifest.exportTo({}).bin).toEqual(`./bin.js`);
+    });
+
+    it(`should preserve bin map if a hash was specified`, () => {
+      const manifest = Manifest.fromText(`{ "name": "name", "bin": { "bin1": "./bin1.js", "bin2": "./bin2.js" } }`);
+      expect(manifest.exportTo({}).bin).toEqual({bin1: `./bin1.js`, bin2: `./bin2.js`});
+    });
+
+    it(`should remove bin if an empty path was specified`, () => {
+      const manifest = Manifest.fromText(`{ "name": "name", "bin": "" }`);
+      expect(manifest.exportTo({}).bin).toEqual(undefined);
+    });
+
+    it(`should remove entries from bin map if an empty path was specified`, () => {
+      const manifest = Manifest.fromText(`{ "name": "name", "bin": { "bin1": " ", "bin2": "./bin2.js" } }`);
+      expect(manifest.exportTo({}).bin).toEqual({bin2: `./bin2.js`});
+    });
   });
 });