doc: rust: improve documentation on cargoLock.lockFile

1 files changed, 9 insertions, 1 deletions

diff --git a/doc/languages-frameworks/rust.section.md b/doc/languages-frameworks/rust.section.md
index f17e1ba8d8f..9de9a06465f 100644
--- a/doc/languages-frameworks/rust.section.md
+++ b/doc/languages-frameworks/rust.section.md
@@ -129,7 +129,15 @@ rustPlatform.buildRustPackage rec {
 ```
 
 This will retrieve the dependencies using fixed-output derivations from
-the specified lockfile.
+the specified lockfile. Note that setting `cargoLock.lockFile` doesn't
+add a `Cargo.lock` to your `src`, and a `Cargo.lock` is still required
+to build a rust package. A simple fix is to use:
+
+```nix
+postPatch = ''
+  cp ${./Cargo.lock} Cargo.lock
+'';
+```
 
 The output hash of each dependency that uses a git source must be
 specified in the `outputHashes` attribute. For example: