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node_modules/cacache/lib/util/move-file.js

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+'use strict'
+
+const fs = require('@npmcli/fs')
+const move = require('@npmcli/move-file')
+const pinflight = require('promise-inflight')
+
+module.exports = moveFile
+
+async function moveFile (src, dest) {
+  const isWindows = process.platform === 'win32'
+
+  // This isn't quite an fs.rename -- the assumption is that
+  // if `dest` already exists, and we get certain errors while
+  // trying to move it, we should just not bother.
+  //
+  // In the case of cache corruption, users will receive an
+  // EINTEGRITY error elsewhere, and can remove the offending
+  // content their own way.
+  //
+  // Note that, as the name suggests, this strictly only supports file moves.
+  try {
+    await fs.link(src, dest)
+  } catch (err) {
+    if (isWindows && err.code === 'EPERM') {
+      // XXX This is a really weird way to handle this situation, as it
+      // results in the src file being deleted even though the dest
+      // might not exist.  Since we pretty much always write files to
+      // deterministic locations based on content hash, this is likely
+      // ok (or at worst, just ends in a future cache miss).  But it would
+      // be worth investigating at some time in the future if this is
+      // really what we want to do here.
+    } else if (err.code === 'EEXIST' || err.code === 'EBUSY') {
+      // file already exists, so whatever
+    } else {
+      throw err
+    }
+  }
+  try {
+    await Promise.all([
+      fs.unlink(src),
+      !isWindows && fs.chmod(dest, '0444'),
+    ])
+  } catch (e) {
+    return pinflight('cacache-move-file:' + dest, async () => {
+      await fs.stat(dest).catch((err) => {
+        if (err.code !== 'ENOENT') {
+          // Something else is wrong here. Bail bail bail
+          throw err
+        }
+      })
+      // file doesn't already exist! let's try a rename -> copy fallback
+      // only delete if it successfully copies
+      return move(src, dest)
+    })
+  }
+}