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authorsterni <sternenseemann@systemli.org>2022-05-26T16·47+0200
committersterni <sternenseemann@systemli.org>2022-06-01T10·30+0000
commitae422c13534d62aae68f06e5e02028dbe6884e33 (patch)
tree3ed4bbd034df7587b7ab68619a2420899f1b7aa4 /users/sterni/nix/misc
parentf54ea857ec5af59fc8c1e2e7219aca523ca1f917 (diff)
feat(sterni/nix/misc): predicate to check if isRestrictedEval r/4198
This is merely a little demonstration of nix#6579:
`users.sterni.nix.misc.isRestrictEval` returns whether the restrict-eval
setting is true or false by exploiting the aforementioned Nix bug.

Change-Id: Icca354d1cd6571cdf0804abae27aac91a18cda1e
Reviewed-on: https://cl.tvl.fyi/c/depot/+/5692
Autosubmit: sterni <sternenseemann@systemli.org>
Reviewed-by: sterni <sternenseemann@systemli.org>
Reviewed-by: tazjin <tazjin@tvl.su>
Tested-by: BuildkiteCI
Diffstat (limited to 'users/sterni/nix/misc')
-rw-r--r--users/sterni/nix/misc/default.nix18
l---------users/sterni/nix/misc/guinea-pig1
2 files changed, 19 insertions, 0 deletions
diff --git a/users/sterni/nix/misc/default.nix b/users/sterni/nix/misc/default.nix
new file mode 100644
index 000000000000..1de9c973ec84
--- /dev/null
+++ b/users/sterni/nix/misc/default.nix
@@ -0,0 +1,18 @@
+{ ... }:
+
+let
+  /* Returns true if it is being evaluated using restrict-eval, false if not.
+     It's more robust than using `builtins.getEnv` since it isn't fooled by
+     `env -i`.
+
+     See https://github.com/NixOS/nix/issues/6579 for a description of the
+     behavior. Precise cause in the evaluator / store implementation is unclear.
+
+     Type: bool
+  */
+  inRestrictedEval = builtins.pathExists (toString ./guinea-pig + "/.");
+in
+
+{
+  inherit inRestrictedEval;
+}
diff --git a/users/sterni/nix/misc/guinea-pig b/users/sterni/nix/misc/guinea-pig
new file mode 120000
index 000000000000..73537e478e3f
--- /dev/null
+++ b/users/sterni/nix/misc/guinea-pig
@@ -0,0 +1 @@
+default.nix
\ No newline at end of file