dockerTools: Add minimal test case for #214434

# this test creates a simple GNU image with docker tools and sees if it executes

import ./make-test-python.nix ({ pkgs, ... }: {

import ./make-test-python.nix ({ pkgs, ... }:

let

  # nixpkgs#214434: dockerTools.buildImage fails to unpack base images

  # containing duplicate rootfs diffs when those duplicate tarballs

  # appear under the manifest's 'Layers'. Docker can generate images

  # like this even though dockerTools does not.

  repeatedLayerTestImage =

    let

      # Rootfs diffs for layers 1 and 2 are identical (and empty)

      layer1 = pkgs.dockerTools.buildImage {  name = "empty";  };

      layer2 = layer1.overrideAttrs (_: { fromImage = layer1; });

      repeatedRootfsDiffs = pkgs.runCommandNoCC "image-with-links.tar" {

        nativeBuildInputs = [pkgs.jq];

      } ''

        mkdir contents

        tar -xf "${layer2}" -C contents

        cd contents

        first_rootfs=$(jq -r '.[0].Layers[0]' manifest.json)

        second_rootfs=$(jq -r '.[0].Layers[1]' manifest.json)

        target_rootfs=$(sha256sum "$first_rootfs" | cut -d' ' -f 1).tar

        # Replace duplicated rootfs diffs with symlinks to one tarball

        chmod -R ug+w .

        mv "$first_rootfs" "$target_rootfs"

        rm "$second_rootfs"

        ln -s "../$target_rootfs" "$first_rootfs"

        ln -s "../$target_rootfs" "$second_rootfs"

        # Update manifest's layers to use the symlinks' target

        cat manifest.json | \

        jq ".[0].Layers[0] = \"$target_rootfs\"" |

        jq ".[0].Layers[1] = \"$target_rootfs\"" > manifest.json.new

        mv manifest.json.new manifest.json

        tar --sort=name --hard-dereference -cf $out .

        '';

    in pkgs.dockerTools.buildImage {

      fromImage = repeatedRootfsDiffs;

      name = "repeated-layer-test";

      copyToRoot = pkgs.bash;

      # A runAsRoot script is required to force previous layers to be unpacked

      runAsRoot = "";

    };

in {

  name = "docker-tools";

  meta = with pkgs.lib.maintainers; {

    maintainers = [ lnl7 roberth ];

            "docker run --rm ${examples.layersUnpackOrder.imageName} cat /layer-order"

        )

    with subtest("Ensure repeated base layers handled by buildImage"):

        docker.succeed(

            "docker load --input='${repeatedLayerTestImage}'",

            "docker run --rm ${repeatedLayerTestImage.imageName} /bin/bash -c 'exit 0'"

        )

    with subtest("Ensure environment variables are correctly inherited"):

        docker.succeed(

            "docker load --input='${examples.environmentVariables}'"