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

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+'use strict'
+
+const fs = require('fs')
+const util = require('util')
+const chmod = util.promisify(fs.chmod)
+const unlink = util.promisify(fs.unlink)
+const stat = util.promisify(fs.stat)
+const move = require('@npmcli/move-file')
+const pinflight = require('promise-inflight')
+
+module.exports = moveFile
+
+function moveFile (src, dest) {
+  const isWindows = global.__CACACHE_TEST_FAKE_WINDOWS__ ||
+    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.
+  return new Promise((resolve, reject) => {
+    fs.link(src, dest, (err) => {
+      if (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.
+          return resolve()
+        } else if (err.code === 'EEXIST' || err.code === 'EBUSY') {
+          // file already exists, so whatever
+          return resolve()
+        } else
+          return reject(err)
+      } else
+        return resolve()
+    })
+  })
+    .then(() => {
+      // content should never change for any reason, so make it read-only
+      return Promise.all([
+        unlink(src),
+        !isWindows && chmod(dest, '0444'),
+      ])
+    })
+    .catch(() => {
+      return pinflight('cacache-move-file:' + dest, () => {
+        return 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)
+        })
+      })
+    })
+}