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authorNaïm Favier <n@monade.li>2023-07-25 15:51:15 +0200
committerNaïm Favier <n@monade.li>2023-07-25 16:09:56 +0200
commit1b756e300f98afe6a583f8bed3acd687d4a8abf9 (patch)
tree18c9eefdb4ff027a7e6044bd62f7bd3fc18e389c /doc
parentae3a7d6ebae80cfab41ef31c03a25926142e8a19 (diff)
doc: clarify release notes about nested attribute merges
Diffstat (limited to 'doc')
-rw-r--r--doc/manual/src/release-notes/rl-2.17.md19
1 files changed, 16 insertions, 3 deletions
diff --git a/doc/manual/src/release-notes/rl-2.17.md b/doc/manual/src/release-notes/rl-2.17.md
index 125a93cfd..0b861aecc 100644
--- a/doc/manual/src/release-notes/rl-2.17.md
+++ b/doc/manual/src/release-notes/rl-2.17.md
@@ -11,8 +11,12 @@
```nix
{
- nested = { foo = 1; };
- nested = { ${"ba" + "r"} = 2; };
+ nested = {
+ foo = 1;
+ };
+ nested = {
+ ${"ba" + "r"} = 2;
+ };
}
```
@@ -22,8 +26,17 @@
{ nested = { bar = 2; foo = 1; }; }
```
- Note that the feature of merging multiple attribute set declarations is of questionable value.
+ Note that the feature of merging multiple *full declarations* of attribute sets like `nested` in the example is of questionable value.
It allows writing expressions that are very hard to read, for instance when there are many lines of code between two declarations of the same attribute.
This has been around for a long time and is therefore supported for backwards compatibility, but should not be relied upon.
+ Instead, consider using the *nested attribute path* syntax:
+
+ ```nix
+ {
+ nested.foo = 1;
+ nested.${"ba" + "r"} = 2;
+ }
+ ```
+
* Tarball flakes can now redirect to an "immutable" URL that will be recorded in lock files. This allows the use of "mutable" tarball URLs like `https://example.org/hello/latest.tar.gz` in flakes. See the [tarball fetcher](../protocols/tarball-fetcher.md) for details.