Support tarballs in nix channel URLs

scripts/nix-channel.in

@@ -6,6 +6,7 @@ use File::Basename;
 use File::Path qw(mkpath);
 use Nix::Config;
 use Nix::Manifest;
+use File::Temp qw(tempdir);
 
 binmode STDERR, ":encoding(utf8)";
 
@@ -98,17 +99,39 @@ sub update {
         my $url = $channels{$name};
         my $origUrl = "$url/MANIFEST";
 
-        # Check if $url is a redirect.  If so, follow it now to ensure
+        # We want to download the url to a file to see if it's a tarball while also checking if we
-        # consistency if the redirection is changed between
+        # got redirected in the process, so that we can grab the various parts of a nix channel
-        # downloading the manifest and the tarball.
+        # definition from a consistent location if the redirect changes mid-download.
-        my $headers = `$Nix::Config::curl --silent --head '$url'`;
+        my $tmpdir = tempdir( CLEANUP => 1 );
+        my $filename;
+        ($url, $filename) = `cd $tmpdir && $Nix::Config::curl --silent --write-out '%{url_effective}\n%{filename_effective}' -L '$url' -O`;
         die "$0: unable to check ‘$url’\n" if $? != 0;
-        $headers =~ s/\r//g;
+        chomp $url;
-        $url = $1 if $headers =~ /^Location:\s*(.*)\s*$/m;
 
+        # If the URL contains a version number, append it to the name
+        # attribute (so that "nix-env -q" on the channels profile
+        # shows something useful).
+        my $cname = $name;
+        $cname .= $1 if basename($url) =~ /(-\d.*)$/;
+
+        my $path;
+        my $ret = -1;
+        if (-e "$tmpdir/$filename") {
+            # Get our temporary download into the store
+            (my $hash, $path) = `PRINT_PATH=1 QUIET=1 $Nix::Config::binDir/nix-prefetch-url 'file://$tmpdir/$filename'`;
+            chomp $path;
+
+            # Try unpacking the expressions to see if they'll be valid for us to process later.
+            # Like anything in nix, this will cache the result so we don't do it again outside of the loop below
+            $ret = system("$Nix::Config::binDir/nix-build --no-out-link -E 'import <nix/unpack-channel.nix> " .
+                          "{ name = \"$cname\"; channelName = \"$name\"; src = builtins.storePath \"$path\"; }'");
+        }
+
+        # The URL doesn't unpack directly, so let's try treating it like a full channel folder with files in it
+        my $extraAttrs = "";
+        if ($ret != 0) {
             # Check if the channel advertises a binary cache.
             my $binaryCacheURL = `$Nix::Config::curl --silent '$url'/binary-cache-url`;
-        my $extraAttrs = "";
             my $getManifest = ($Nix::Config::config{"force-manifest"} // "false") eq "true";
             if ($? == 0 && $binaryCacheURL ne "") {
                 $extraAttrs .= "binaryCacheURL = \"$binaryCacheURL\"; ";
@@ -131,16 +154,12 @@ sub update {
             system("$Nix::Config::curl --fail --silent --head '$fullURL' > /dev/null") == 0 or
                 $fullURL = "$url/nixexprs.tar.bz2";
             print STDERR "downloading Nix expressions from ‘$fullURL’...\n";
-        my ($hash, $path) = `PRINT_PATH=1 QUIET=1 $Nix::Config::binDir/nix-prefetch-url '$fullURL'`;
+            (my $hash, $path) = `PRINT_PATH=1 QUIET=1 $Nix::Config::binDir/nix-prefetch-url '$fullURL'`;
             die "cannot fetch ‘$fullURL’\n" if $? != 0;
             chomp $path;
+        }
 
-        # If the URL contains a version number, append it to the name
+        # Regardless of where it came from, add the expression representing this channel to accumulated expression
-        # attribute (so that "nix-env -q" on the channels profile
-        # shows something useful).
-        my $cname = $name;
-        $cname .= $1 if basename($url) =~ /(-\d.*)$/;
-
         $exprs .= "'f: f { name = \"$cname\"; channelName = \"$name\"; src = builtins.storePath \"$path\"; $extraAttrs }' ";
     }
 

tests/nix-channel.sh

@@ -41,3 +41,26 @@ grep -q 'item.*attrPath="foo".*name="dependencies"' $TEST_ROOT/meta.xml
 # Do an install.
 nix-env -i dependencies
 [ -e $TEST_ROOT/var/nix/profiles/default/foobar ]
+
+
+
+clearProfiles
+clearManifests
+rm -f $TEST_ROOT/.nix-channels
+
+# Test updating from a tarball
+nix-channel --add file://$TEST_ROOT/foo/nixexprs.tar.bz2
+nix-channel --update
+
+# Do a query.
+nix-env -qa \* --meta --xml --out-path > $TEST_ROOT/meta.xml
+if [ "$xmllint" != false ]; then
+    $xmllint --noout $TEST_ROOT/meta.xml || fail "malformed XML"
+fi
+grep -q 'meta.*description.*Random test package' $TEST_ROOT/meta.xml
+grep -q 'item.*attrPath="foo".*name="dependencies"' $TEST_ROOT/meta.xml
+
+# Do an install.
+nix-env -i dependencies
+[ -e $TEST_ROOT/var/nix/profiles/default/foobar ]
+