writers.makeScriptWriter: fix on Darwin\MacOS (#93757)

adrian-gierakowski · web-flow · commit a6133b7a3968 · 2020-07-25T11:47:20.000+02:00
* writers.makeScriptWriter: fix on Darwin\MacOS On Darwin a script cannot be used as an interpreter in a shebang line, which causes scripts produced with makeScriptWriter (and its derivatives) to fail at run time if the used interpreter was wrapped with makeWrapper (as in the case of python3.withPackages). This commit fixes the problem by detecting if the interpreter is a script and prepending its shebang to the final interpreter line. For example if used interpreter is; ``` /nix/store/ynwv137n2650qy39swcflxbcygk5jwv1-python3-3.8.3-env/bin/python ``` which is a script with following shebang: ``` #! /nix/store/knd85yc7iwli8344ghav3zli8d9gril0-bash-4.4-p23/bin/bash -e ``` then the shebang line in the produced script will be ``` #! /nix/store/knd85yc7iwli8344ghav3zli8d9gril0-bash-4.4-p23/bin/bash -e /nix/store/ynwv137n2650qy39swcflxbcygk5jwv1-python3-3.8.3-env/bin/python ``` This works on Darwin since there does not seem to be a limit to the length of the shabang line and the shebang lines support multiple arguments to the interpreters (as opposed to linux where the kernel imposes a strict limit on shebang lengh and everything following the interpreter is passed to it as a single string). fixes; #93609 related to: #65351 #11133 (and probably a bunch of others) NOTE: scripts produced on platforms other than Darwin will remain unmodified by this PR. However it might worth considering extending this fix to BSD systems in general. I didn't do it since I have no way of testing it on systems other than MacOS and linux. * writers.makeScriptWriter: fix typo in comment * writers.makeScriptWriter: fail build if interpreter of interpreter is a script
diff --git a/pkgs/build-support/writers/default.nix b/pkgs/build-support/writers/default.nix
@@ -22,7 +22,30 @@ rec {
       inherit interpreter;
       contentPath = content;
     }) ''
-      echo "#! $interpreter" > $out
+      # On darwin a script cannot be used as an interpreter in a shebang but
+      # there doesn't seem to be a limit to the size of shebang and multiple
+      # arguments to the interpreter are allowed.
+      if [[ -n "${toString pkgs.stdenvNoCC.isDarwin}" ]] && isScript $interpreter
+      then
+        wrapperInterpreterLine=$(head -1 "$interpreter" | tail -c+3)
+        # Get first word from the line (note: xargs echo remove leading spaces)
+        wrapperInterpreter=$(echo "$wrapperInterpreterLine" | xargs echo | cut -d " " -f1)
+
+        if isScript $wrapperInterpreter
+        then
+          echo "error: passed interpreter ($interpreter) is a script which has another script ($wrapperInterpreter) as an interpreter, which is not supported."
+          exit 1
+        fi
+
+        # This should work as long as wrapperInterpreter is a shell, which is
+        # the case for programs wrapped with makeWrapper, like
+        # python3.withPackages etc.
+        interpreterLine="$wrapperInterpreterLine $interpreter"
+      else
+        interpreterLine=$interpreter
+      fi
+
+      echo "#! $interpreterLine" > $out
       cat "$contentPath" >> $out
       ${optionalString (check != "") ''
         ${check} $out
