Mention number of derivations to be build/fetched in output

Also correct grammar for the case of a single derivation.

4 files changed, 21 insertions, 9 deletions

diff --git a/doc/manual/advanced-topics/diff-hook.xml b/doc/manual/advanced-topics/diff-hook.xml
index fb4bf819f..f01ab71b3 100644
--- a/doc/manual/advanced-topics/diff-hook.xml
+++ b/doc/manual/advanced-topics/diff-hook.xml
@@ -70,7 +70,7 @@ path just built.</para>
 
   <screen>
 $ nix-build ./deterministic.nix -A stable
-these derivations will be built:
+this derivation will be built:
   /nix/store/z98fasz2jqy9gs0xbvdj939p27jwda38-stable.drv
 building '/nix/store/z98fasz2jqy9gs0xbvdj939p27jwda38-stable.drv'...
 /nix/store/yyxlzw3vqaas7wfp04g0b1xg51f2czgq-stable
@@ -85,7 +85,7 @@ checking outputs of '/nix/store/z98fasz2jqy9gs0xbvdj939p27jwda38-stable.drv'...
 
   <screen>
 $ nix-build ./deterministic.nix -A unstable
-these derivations will be built:
+this derivation will be built:
   /nix/store/cgl13lbj1w368r5z8gywipl1ifli7dhk-unstable.drv
 building '/nix/store/cgl13lbj1w368r5z8gywipl1ifli7dhk-unstable.drv'...
 /nix/store/krpqk0l9ib0ibi1d2w52z293zw455cap-unstable
@@ -193,7 +193,7 @@ repeat = 1
     An example output of this configuration:
     <screen>
 $ nix-build ./test.nix -A unstable
-these derivations will be built:
+this derivation will be built:
   /nix/store/ch6llwpr2h8c3jmnf3f2ghkhx59aa97f-unstable.drv
 building '/nix/store/ch6llwpr2h8c3jmnf3f2ghkhx59aa97f-unstable.drv' (round 1/2)...
 building '/nix/store/ch6llwpr2h8c3jmnf3f2ghkhx59aa97f-unstable.drv' (round 2/2)...
diff --git a/doc/manual/advanced-topics/post-build-hook.xml b/doc/manual/advanced-topics/post-build-hook.xml
index acfe9e3cc..6cc286ee1 100644
--- a/doc/manual/advanced-topics/post-build-hook.xml
+++ b/doc/manual/advanced-topics/post-build-hook.xml
@@ -122,7 +122,7 @@ post-build-hook = /etc/nix/upload-to-cache.sh
 
   <screen>
 $ nix-build -E '(import &lt;nixpkgs&gt; {}).writeText "example" (builtins.toString builtins.currentTime)'
-these derivations will be built:
+this derivation will be built:
   /nix/store/s4pnfbkalzy5qz57qs6yybna8wylkig6-example.drv
 building '/nix/store/s4pnfbkalzy5qz57qs6yybna8wylkig6-example.drv'...
 running post-build-hook '/home/grahamc/projects/github.com/NixOS/nix/post-hook.sh'...
diff --git a/doc/manual/command-ref/nix-env.xml b/doc/manual/command-ref/nix-env.xml
index 2b95b6819..55f25d959 100644
--- a/doc/manual/command-ref/nix-env.xml
+++ b/doc/manual/command-ref/nix-env.xml
@@ -516,7 +516,7 @@ source:
 $ nix-env -f '&lt;nixpkgs>' -iA hello --dry-run
 (dry run; not doing anything)
 installing ‘hello-2.10’
-these paths will be fetched (0.04 MiB download, 0.19 MiB unpacked):
+this path will be fetched (0.04 MiB download, 0.19 MiB unpacked):
   /nix/store/wkhdf9jinag5750mqlax6z2zbwhqb76n-hello-2.10
   <replaceable>...</replaceable></screen>
 
diff --git a/src/libmain/shared.cc b/src/libmain/shared.cc
index dc6d5e413..1cb422967 100644
--- a/src/libmain/shared.cc
+++ b/src/libmain/shared.cc
@@ -48,7 +48,10 @@ void printMissing(ref<Store> store, const StorePathSet & willBuild,
     unsigned long long downloadSize, unsigned long long narSize, Verbosity lvl)
 {
     if (!willBuild.empty()) {
-        printMsg(lvl, "these derivations will be built:");
+        if (willBuild.size() == 1)
+            printMsg(lvl, fmt("this derivation will be built:"));
+        else
+            printMsg(lvl, fmt("these %d derivations will be built:", willBuild.size()));
         auto sorted = store->topoSortPaths(willBuild);
         reverse(sorted.begin(), sorted.end());
         for (auto & i : sorted)
@@ -56,9 +59,18 @@ void printMissing(ref<Store> store, const StorePathSet & willBuild,
     }
 
     if (!willSubstitute.empty()) {
-        printMsg(lvl, fmt("these paths will be fetched (%.2f MiB download, %.2f MiB unpacked):",
-                downloadSize / (1024.0 * 1024.0),
-                narSize / (1024.0 * 1024.0)));
+        const float downloadSizeMiB = downloadSize / (1024.f * 1024.f);
+        const float narSizeMiB = narSize / (1024.f * 1024.f);
+        if (willSubstitute.size() == 1) {
+            printMsg(lvl, fmt("this path will be fetched (%.2f MiB download, %.2f MiB unpacked):",
+                downloadSizeMiB,
+                narSizeMiB));
+        } else {
+            printMsg(lvl, fmt("these %d paths will be fetched (%.2f MiB download, %.2f MiB unpacked):",
+                willSubstitute.size(),
+                downloadSizeMiB,
+                narSizeMiB));
+        }
         for (auto & i : willSubstitute)
             printMsg(lvl, fmt("  %s", store->printStorePath(i)));
     }