Fix #1435 (failing dependencies of optional dependencies)

__tests__/commands/install/integration.js

@@ -823,6 +823,14 @@ test.concurrent('install a module with incompatible optional dependency should s
     });
   });
 
+test.concurrent('install a module with optional dependency should skip incompatible transient dependency',
+  (): Promise<void> => {
+    return runInstall({}, 'install-should-skip-incompatible-optional-sub-dep', async (config) => {
+      assert.ok(await fs.exists(path.join(config.cwd, 'node_modules', 'dep-optional')));
+      assert.ok(!(await fs.exists(path.join(config.cwd, 'node_modules', 'dep-incompatible'))));
+    });
+  });
+
 // this tests for a problem occuring due to optional dependency incompatible with os, in this case fsevents
 // this would fail on os's incompatible with fsevents, which is everything except osx.
 if (process.platform !== 'darwin') {
@@ -843,6 +851,14 @@ test.concurrent('optional dependency that fails to build should not be installed
     });
   });
 
+test.concurrent('failing dependency of optional dependency should not be installed',
+  (): Promise<void> => {
+    return runInstall({}, 'should-not-install-failing-deps-of-optional-deps', async (config) => {
+      assert.equal(await fs.exists(path.join(config.cwd, 'node_modules', 'optional-dep')), true);
+      assert.equal(await fs.exists(path.join(config.cwd, 'node_modules', 'sub-failing')), false);
+    });
+  });
+
 // Covers current behavior, issue opened whether this should be changed https://github.com/yarnpkg/yarn/issues/2274
 test.concurrent('a subdependency of an optional dependency that fails should be installed',
   (): Promise<void> => {

__tests__/fixtures/install/install-should-skip-incompatible-optional-sub-dep/.npmrc

@@ -0,0 +1 @@
+yarn-offline-mirror=./mirror-for-offline

__tests__/fixtures/install/install-should-skip-incompatible-optional-sub-dep/package.json

@@ -0,0 +1,5 @@
+{
+  "optionalDependencies": {
+    "dep-optional": "1.0.0"
+  }
+}

__tests__/fixtures/install/install-should-skip-incompatible-optional-sub-dep/yarn.lock

@@ -0,0 +1,11 @@
+# THIS IS AN AUTOGENERATED FILE. DO NOT EDIT THIS FILE DIRECTLY.
+# yarn lockfile v1
+[email protected]:
+  version "1.0.0"
+  resolved dep-optional-1.0.0.tgz#c8cbcee6f23932e14898a2dd4c76e38b37d31531
+  dependencies:
+    dep-incompatible "1.0.0"
+
+[email protected]:
+  version "1.0.0"
+  resolved dep-incompatible-1.0.0.tgz#f711458d716eeb5c2cbbc11ee09edccedbb79e74

__tests__/fixtures/install/should-not-install-failing-deps-of-optional-deps/optional-dep/install.js

@@ -0,0 +1 @@
+process.exit(0);

__tests__/fixtures/install/should-not-install-failing-deps-of-optional-deps/optional-dep/package.json

@@ -0,0 +1,10 @@
+{
+  "name": "optional-failing",
+  "version": "0.0.0",
+  "scripts": {
+    "install": "node install.js"
+  },
+  "dependencies": {
+    "sub-failing": "file:../sub-failing"
+  }
+}

__tests__/fixtures/install/should-not-install-failing-deps-of-optional-deps/package.json

@@ -0,0 +1,5 @@
+{
+  "optionalDependencies": {
+    "optional-dep": "file:optional-dep"
+  }
+}

__tests__/fixtures/install/should-not-install-failing-deps-of-optional-deps/sub-failing/install.js

@@ -0,0 +1 @@
+process.exit(1);

__tests__/fixtures/install/should-not-install-failing-deps-of-optional-deps/sub-failing/package.json

@@ -0,0 +1,7 @@
+{
+  "name": "sub-failing",
+  "version": "0.0.0",
+  "scripts": {
+    "install": "node install.js"
+  }
+}

src/package-request.js

@@ -281,7 +281,8 @@ export default class PackageRequest {
       promises.push(this.resolver.find({
         pattern: depPattern,
         registry: remote.registry,
-        optional: false,
+        // dependencies of optional dependencies should themselves be optional
+        optional: this.optional,
         parentRequest: this,
       }));
     }