fix(linking): Dont integrity check build artifacts

__tests__/commands/add.js

@@ -1062,6 +1062,40 @@ test.concurrent('should retain build artifacts after add', async () => {
   );
 });
 
+// If an install script changed a file that was installed with the package,
+// then all subsequent yarn commands (like add) would see the file as changed, marking
+// the package as "fresh" and re-running install scripts.
+// The fix was to not mark a package as "fresh" if a changed file was also a build artifact.
+// This test writes the current timestamp to a file tht also existed in the package.
+// The timestamp generated by package A shouldn't change when adding package B.
+// See: https://github.com/yarnpkg/yarn/issues/932#issuecomment-370245462
+test.concurrent('should not run scripts if build artifact changed', async () => {
+  await buildRun(
+    reporters.BufferReporter,
+    fixturesLoc,
+    async (args, flags, config, reporter, lockfile): Promise<void> => {
+      const addA = new Add(args, flags, config, reporter, lockfile);
+      await addA.init();
+
+      const artifactFile = path.join(config.cwd, 'node_modules', 'a', 'foo.txt');
+
+      const beforeContents = await fs.readFileAny([artifactFile]);
+
+      // re-read lockfile after the first `add` or else it will still be empty
+      lockfile = await Lockfile.fromDirectory(config.cwd);
+
+      const addB = new Add(['file:b'], flags, config, reporter, lockfile);
+      await addB.init();
+
+      const afterContents = await fs.readFileAny([artifactFile]);
+      expect(afterContents).toEqual(beforeContents);
+    },
+    ['file:a'],
+    {},
+    'retain-build-artifacts-after-add',
+  );
+});
+
 test.concurrent('installing with --pure-lockfile and then adding should keep build artifacts', async () => {
   const fixture = 'integrity-pure-lockfile';
 

__tests__/fixtures/add/retain-build-artifacts-after-add/a/foo.txt

@@ -0,0 +1 @@
+X

__tests__/fixtures/add/retain-build-artifacts-after-add/a/install.js

@@ -1 +1 @@
-require('fs').writeFileSync('foo.txt', 'foobar');
+require('fs').writeFileSync('foo.txt', new Date().getTime());

src/reporters/lang/en.js

@@ -52,6 +52,7 @@ const messages = {
   verboseFileRemoveExtraneous: 'Removing extraneous file $0.',
   verboseFilePhantomExtraneous:
     "File $0 would be marked as extraneous but has been removed as it's listed as a phantom file.",
+  verboseFileSkipArtifact: 'Skipping copying of $0 as the file is marked as a built artifact and subject to change.',
   verboseFileFolder: 'Creating directory $0.',
 
   verboseRequestStart: 'Performing $0 request to $1.',

src/util/fs.js

@@ -276,6 +276,13 @@ async function buildActionsForCopy(
         } catch (err) {}
       } */
 
+      if (bothFiles && artifactFiles.has(dest)) {
+        // this file gets changed during build, likely by a custom install script. Don't bother checking it.
+        onDone();
+        reporter.verbose(reporter.lang('verboseFileSkipArtifact', src));
+        return;
+      }
+
       if (bothFiles && srcStat.size === destStat.size && fileDatesEqual(srcStat.mtime, destStat.mtime)) {
         // we can safely assume this is the same file
         onDone();
@@ -467,6 +474,13 @@ async function buildActionsForHardlink(
         }
       }
 
+      if (bothFiles && artifactFiles.has(dest)) {
+        // this file gets changed during build, likely by a custom install script. Don't bother checking it.
+        onDone();
+        reporter.verbose(reporter.lang('verboseFileSkipArtifact', src));
+        return;
+      }
+
       // correct hardlink
       if (bothFiles && srcStat.ino !== null && srcStat.ino === destStat.ino) {
         onDone();