From 762273f1fd48b2b2f2bbedca65abfd4c07b5af05 Mon Sep 17 00:00:00 2001
From: Matthew Bauer <mjbauer95@gmail.com>
Date: Tue, 9 Jun 2020 01:23:37 -0500
Subject: [PATCH] Allow empty hash in derivations
follow up of https://github.com/NixOS/nix/pull/3544
This allows hash="" so that it can be used for debugging purposes. For
instance, this gives you an error message like:
warning: found empty hash, assuming you wanted 'sha256:0000000000000000000000000000000000000000000000000000'
hash mismatch in fixed-output derivation '/nix/store/asx6qw1r1xk6iak6y6jph4n58h4hdmbm-nix':
wanted: sha256:0000000000000000000000000000000000000000000000000000
got: sha256:0fpfhipl9v1mfzw2ffmxiyyzqwlkvww22bh9wcy4qrfslb4jm429
---
src/libexpr/primops.cc | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/src/libexpr/primops.cc b/src/libexpr/primops.cc
index d458ab272..de04fd2be 100644
--- a/src/libexpr/primops.cc
+++ b/src/libexpr/primops.cc
@@ -719,7 +719,13 @@ static void prim_derivationStrict(EvalState & state, const Pos & pos, Value * *
throw Error(format("multiple outputs are not supported in fixed-output derivations, at %1%") % posDrvName);
HashType ht = outputHashAlgo.empty() ? htUnknown : parseHashType(outputHashAlgo);
- Hash h(*outputHash, ht);
+
+ Hash h;
+ if (outputHash->empty()) {
+ h = Hash(ht);
+ printError("warning: found empty hash, assuming you wanted '%s'", h.to_string());
+ } else
+ h = Hash(*outputHash, ht);
auto outPath = state.store->makeFixedOutputPath(ingestionMethod, h, drvName);
if (!jsonObject) drv.env["out"] = state.store->printStorePath(outPath);
--
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