_7zz: speculatively try unpacking any file (#566897)

pkgs/by-name/_7/_7zz/package.nix

@@ -22,6 +22,7 @@
 
   # For tests
   testers,
+  fetchurl,
 }:
 
 let
@@ -165,9 +166,83 @@ stdenv.mkDerivation (finalAttrs: {
         extraArgs = [ "--version=skip" ];
       })
     ];
-    tests.version = testers.testVersion {
-      package = finalAttrs.finalPackage;
-      command = "7zz --help";
+    tests = {
+      version = testers.testVersion {
+        package = finalAttrs.finalPackage;
+        command = "7zz --help";
+      };
+      # So dmg can be tested on Linux without
+      # macos toolchains
+      undmg = stdenv.mkDerivation {
+        pname = "test-undmg";
+        version = "none";
+
+        src = fetchurl {
+          url = "https://caido.download/releases/v0.57.0/caido-desktop-v0.57.0-mac-aarch64.dmg";
+          hash = "sha256-GmpMnaGR7gYz1RvSO5xj9AA3xU1mn2IBInakmVkuG7A=";
+        };
+
+        nativeBuildInputs = [
+          finalAttrs.finalPackage
+        ];
+
+        buildPhase = ''
+          if [[ ! -e Contents ]]; then
+            # Should exist
+            ls
+            exit 1
+          fi
+        '';
+        installPhase = "touch $out";
+      };
+
+      unzip = stdenv.mkDerivation {
+        pname = "test-unzip";
+        version = "none";
+
+        src = fetchurl {
+          url = "mirror://sourceforge/libjson/libjson_7.6.1.zip";
+          hash = "sha256-ByZ6OVEDjuLgLSbMQb+OJ1Zow491EkDT543JeRguc3Y=";
+        };
+
+        nativeBuildInputs = [
+          finalAttrs.finalPackage
+        ];
+
+        buildPhase = ''
+          if [[ ! -e libjson.h ]]; then
+            # Should exist
+            ls
+            exit 1
+          fi
+        '';
+        installPhase = "touch $out";
+      };
+
+      # We do not want to decompress tarballs since
+      # it will just leave an uncompressed tarball in the source dir.
+      tarballs = stdenv.mkDerivation {
+        pname = "test-tarball";
+        version = "none";
+
+        src = fetchurl {
+          url = "https://github.com/ip7z/7zip/archive/refs/tags/26.04.tar.gz";
+          hash = "sha256-SP3G3+h57i24Z7sH8ZxKlAa/6gHVH0h4W2x6E3iB4lw=";
+        };
+
+        nativeBuildInputs = [
+          finalAttrs.finalPackage
+        ];
+
+        buildPhase = ''
+          if [[ ! -e README.md ]]; then
+            # Should exist
+            ls
+            exit 1
+          fi
+        '';
+        installPhase = "touch $out";
+      };
     };
   };
 

pkgs/by-name/_7/_7zz/setup-hook.sh

@@ -1,5 +1,27 @@
-unpackCmdHooks+=(_tryUnpackDmg)
-_tryUnpackDmg() {
-    if ! [[ "$curSrc" =~ \.dmg$ ]]; then return 1; fi
-    7zz x -sns- -snld "$curSrc"
+unpackCmdHooks+=(_tryUnpack7zip)
+
+# 7zip supports unpacking many formats.
+# No need to implement our own inaccurate extension-based detection.
+_tryUnpack7zip() {
+  local mime="$(file -zb --mime-type "$curSrc")"
+
+  if [[ "$mime" == "application/x-tar" ]]; then
+    # Compressed tarballs should use tar instead, and 7zip doesn't
+    # recursively unpack. So it would just leave a .tar file in
+    # the build directory
+    return 1
+  fi
+
+  local flags=(
+    "-bso0" # Disable stdout
+    "-bsp0" # Disable progress output
+    "-bse0" # Disable stderr output
+    "-sns-" # Ignore auxilliary filesystem streams
+    # Allow 'dangerous' links, which are links that include '..'
+    # This does not include absolute paths and links that escape the archive,
+    # those require a higher 'dangerous level'.
+    "-snld"
+    "-y" # Accept all prompts
+  )
+  7zz x "${flags[@]}" "$curSrc"
 }