feat(shell): add unset command

.yarn/versions/2f8bb76f.yml

@@ -0,0 +1,35 @@
+releases:
+  "@yarnpkg/cli": patch
+  "@yarnpkg/core": patch
+  "@yarnpkg/shell": 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-shell/sources/index.ts

@@ -166,6 +166,19 @@ const BUILTINS = new Map<string, ShellBuiltin>([
     return await setTimeout(1000 * seconds, 0);
   }],
 
+  [`unset`, async ([name, ...rest]: Array<string>, opts: ShellOptions, state: ShellState) => {
+    if (typeof name === `undefined`)
+      throw new ShellError(`unset: missing name`);
+
+    if (!Object.hasOwn(state.environment, name) && !Object.hasOwn(state.variables, name))
+      throw new ShellError(`unset: unbound variable "${name}"`);
+
+    delete state.environment[name];
+    delete state.variables[name];
+
+    return 0;
+  }],
+
   [`__ysh_run_procedure`, async (args: Array<string>, opts: ShellOptions, state: ShellState) => {
     const procedure = state.procedures[args[0]];
 

packages/yarnpkg-shell/tests/shell.test.ts

@@ -2094,5 +2094,34 @@ describe(`Shell`, () => {
         });
       });
     });
+
+    describe(`unset`, () => {
+      it(`should throw a recoverable error when the variable name is missing`, async () => {
+        await expectResult(bufferResult(
+          `unset`,
+        ), {
+          exitCode: 1,
+          stderr: `unset: missing name\n`,
+        });
+      });
+
+      it(`should throw a recoverable error when the variable is unbound`, async () => {
+        await expectResult(bufferResult(
+          `unset FOO`,
+        ), {
+          exitCode: 1,
+          stderr: `unset: unbound variable "FOO"\n`,
+        });
+      });
+
+      it(`should unset the variable`, async () => {
+        await expectResult(bufferResult(
+          `FOO=bar; unset FOO; echo $FOO`,
+        ), {
+          exitCode: 1,
+          stderr: `Unbound variable "FOO"\n`,
+        });
+      });
+    });
   });
 });