feat: update flatten to deduplicate files

distroless/private/flatten.sh

@@ -17,7 +17,6 @@ if [[ "$output" != "-" ]]; then
         fi
     done
 
-
     # There not a lot happening here but there is still too many implicit knowledge.
     # 
     # When we run bsdtar, we ask for it to prompt every entry, in the same order we created above, the mtree.
@@ -29,21 +28,26 @@ if [[ "$output" != "-" ]]; then
     # See: https://github.com/libarchive/libarchive/blob/f745a848d7a81758cd9fcd49d7fd45caeebe1c3d/tar/util.c#L240
     # See: https://github.com/libarchive/libarchive/blob/f745a848d7a81758cd9fcd49d7fd45caeebe1c3d/tar/util.c#L216
     # 
-    # And finally we iterate over all the entries generating 31 bytes of interleaved 'Y' or 'N' date based on if 
-    # we came across the entry before, for directories the first occurrence is kept, and for files copies are 
-    # preserved.
+    # To match the extraction behavior of tar itself, we want to preserve only the final occurrence of each file
+    # and directory in the archive. To do this, we iterate over all the entries twice. The first pass computes the
+    # number of occurrences of each path, and the second pass determines whether each entry is the final (or only)
+    # occurrence of that path.
+
     $bsdtar --confirmation "$@" > $output 2< <(awk '{
-        if (substr($0,0,1) == "#") {
-            next;
-        }
         count[$1]++;
+        files[NR] = $1
+     }
+     END {
         ORS=""
-        keep="n"
-        if (count[$1] == 1 || $1 !~ "/$") {
-            keep="y"
+        for (i=1; i<=NR; i++) {
+            seen[files[i]]++
+            keep="n"
+            if (count[files[i]] == seen[files[i]]) {
+                keep="y"
+            }
+            for (j=0; j<31; j++) print keep
+            fflush()
         }
-        for (i=0;i<31;i++) print keep
-        fflush() 
     }' "$mtree")
     rm "$mtree"
 else 

distroless/tests/asserts.bzl

@@ -3,16 +3,58 @@
 load("@aspect_bazel_lib//lib:diff_test.bzl", "diff_test")
 load("@bazel_skylib//rules:write_file.bzl", "write_file")
 
-# buildifier: disable=function-docstring
+def assert_tar_mtree(name, actual, expected):
+    """
+    Assert that an mtree representation of a tarball matches an expected value.
+
+    Args:
+        name: name of this assertion
+        actual: label for a tarball
+        expected: expected mtree
+    """
+    actual_mtree = "_{}_mtree".format(name)
+    expected_mtree = "_{}_expected".format(name)
+
+    native.genrule(
+        name = actual_mtree,
+        srcs = [actual],
+        outs = ["_{}.mtree".format(name)],
+        cmd = "cat $(execpath {}) | $(BSDTAR_BIN) -cf $@ --format=mtree --options '!nlink' @-".format(actual),
+        toolchains = ["@bsd_tar_toolchains//:resolved_toolchain"],
+    )
+
+    write_file(
+        name = expected_mtree,
+        out = "_{}.expected".format(name),
+        content = [expected],
+        newline = "unix",
+    )
+
+    diff_test(
+        name = name,
+        file1 = actual_mtree,
+        file2 = expected_mtree,
+        timeout = "short",
+    )
+
+
 def assert_tar_listing(name, actual, expected):
+    """
+    Assert that the listed contents of a tarball match an expected value. This is useful when checking for duplicated paths.
+
+    Args:
+        name: name of this assertion
+        actual: label for a tarball
+        expected: expected listing
+    """
     actual_listing = "_{}_listing".format(name)
     expected_listing = "_{}_expected".format(name)
 
     native.genrule(
         name = actual_listing,
         srcs = [actual],
         outs = ["_{}.listing".format(name)],
-        cmd = "cat $(execpath {}) | $(BSDTAR_BIN) -cf $@ --format=mtree --options '!nlink' @-".format(actual),
+        cmd = "cat $(execpath {}) | $(BSDTAR_BIN) -tf - > $@".format(actual),
         toolchains = ["@bsd_tar_toolchains//:resolved_toolchain"],
     )
 

examples/cacerts/BUILD.bazel

@@ -1,12 +1,12 @@
 load("//distroless:defs.bzl", "cacerts")
-load("//distroless/tests:asserts.bzl", "assert_tar_listing")
+load("//distroless/tests:asserts.bzl", "assert_tar_mtree")
 
 cacerts(
     name = "cacerts",
     package = "@example-bullseye-ca-certificates//:data.tar.xz",
 )
 
-assert_tar_listing(
+assert_tar_mtree(
     name = "test_cacerts",
     actual = "cacerts",
     expected = """\

examples/flatten/BUILD.bazel

@@ -1,6 +1,6 @@
 load("@aspect_bazel_lib//lib:tar.bzl", "tar")
 load("//distroless:defs.bzl", "flatten", "home", "passwd")
-load("//distroless/tests:asserts.bzl", "assert_tar_listing")
+load("//distroless/tests:asserts.bzl", "assert_tar_listing", "assert_tar_mtree")
 
 passwd(
     name = "passwd",
@@ -47,7 +47,7 @@ flatten(
     ],
 )
 
-assert_tar_listing(
+assert_tar_mtree(
     name = "test_flatten",
     actual = "flatten",
     expected = """\
@@ -94,8 +94,8 @@ flatten(
     ],
 )
 
-assert_tar_listing(
-    name = "test_flatten_dedup",
+assert_tar_mtree(
+    name = "test_flatten_dedup_mtree",
     actual = "flatten_dedup",
     expected = """\
 #mtree
@@ -107,3 +107,17 @@ assert_tar_listing(
 ./examples/flatten/dir/sub/content.txt time=1672560000.0 mode=755 gid=0 uid=0 type=file size=0
 """,
 )
+
+assert_tar_listing(
+    name = "test_flatten_dedup_listing",
+    actual = "flatten_dedup",
+    expected = """\
+examples/
+examples/flatten/
+examples/flatten/dir/
+examples/flatten/dir/changelog
+examples/flatten/dir/sub/
+examples/flatten/dir/sub/content.txt
+""",
+)
+

examples/group/BUILD.bazel

@@ -1,6 +1,6 @@
 load("@aspect_bazel_lib//lib:diff_test.bzl", "diff_test")
 load("//distroless:defs.bzl", "group")
-load("//distroless/tests:asserts.bzl", "assert_tar_listing")
+load("//distroless/tests:asserts.bzl", "assert_tar_mtree")
 
 group(
     name = "group",
@@ -32,7 +32,7 @@ diff_test(
     file2 = "group.expected.txt",
 )
 
-assert_tar_listing(
+assert_tar_mtree(
     name = "test_group",
     actual = "group",
     expected = """\

examples/home/BUILD.bazel

@@ -1,5 +1,5 @@
 load("//distroless:defs.bzl", "home")
-load("//distroless/tests:asserts.bzl", "assert_tar_listing")
+load("//distroless/tests:asserts.bzl", "assert_tar_mtree")
 
 home(
     name = "home",
@@ -17,7 +17,7 @@ home(
     ],
 )
 
-assert_tar_listing(
+assert_tar_mtree(
     name = "test_home",
     actual = "home",
     expected = """\

examples/java_keystore/BUILD.bazel

@@ -1,5 +1,5 @@
 load("//distroless:defs.bzl", "java_keystore")
-load("//distroless/tests:asserts.bzl", "assert_jks_listing", "assert_tar_listing")
+load("//distroless/tests:asserts.bzl", "assert_jks_listing", "assert_tar_mtree")
 
 java_keystore(
     name = "java_keystore",
@@ -23,7 +23,7 @@ assert_jks_listing(
     expected = "expected.jks.output",
 )
 
-assert_tar_listing(
+assert_tar_mtree(
     name = "test_java_keystore",
     actual = "java_keystore",
     expected = """\

examples/locale/BUILD.bazel

@@ -1,13 +1,13 @@
 load("//distroless:defs.bzl", "locale")
-load("//distroless/tests:asserts.bzl", "assert_tar_listing")
+load("//distroless/tests:asserts.bzl", "assert_tar_mtree")
 
 locale(
     name = "bullseye",
     charset = "C.UTF-8",
     package = "@example-bullseye-libc-bin//:data.tar.xz",
 )
 
-assert_tar_listing(
+assert_tar_mtree(
     name = "test_bullseye",
     actual = "bullseye",
     expected = """\
@@ -41,7 +41,7 @@ locale(
     package = "@example-bookworm-libc-bin//:data.tar.xz",
 )
 
-assert_tar_listing(
+assert_tar_mtree(
     name = "test_bookworm",
     actual = "bookworm",
     expected = """\

examples/os_release/BUILD.bazel

@@ -1,6 +1,6 @@
 load("@aspect_bazel_lib//lib:diff_test.bzl", "diff_test")
 load("//distroless:defs.bzl", "os_release")
-load("//distroless/tests:asserts.bzl", "assert_tar_listing")
+load("//distroless/tests:asserts.bzl", "assert_tar_mtree")
 
 os_release(
     name = "os_release",
@@ -16,7 +16,7 @@ diff_test(
     file2 = "content.expected.txt",
 )
 
-assert_tar_listing(
+assert_tar_mtree(
     name = "test_os_release",
     actual = "os_release",
     expected = """\
@@ -37,7 +37,7 @@ os_release(
     path = "/etc/os-release",
 )
 
-assert_tar_listing(
+assert_tar_mtree(
     name = "test_os_release_alternative_path",
     actual = "os_release_alternative_path",
     expected = """\

examples/passwd/BUILD.bazel

@@ -1,6 +1,6 @@
 load("@aspect_bazel_lib//lib:diff_test.bzl", "diff_test")
 load("//distroless:defs.bzl", "passwd")
-load("//distroless/tests:asserts.bzl", "assert_tar_listing")
+load("//distroless/tests:asserts.bzl", "assert_tar_mtree")
 
 passwd(
     name = "passwd",
@@ -22,7 +22,7 @@ diff_test(
     file2 = "passwd.expected.txt",
 )
 
-assert_tar_listing(
+assert_tar_mtree(
     name = "test_passwd",
     actual = "passwd",
     expected = """\

examples/statusd/BUILD.bazel

@@ -1,14 +1,14 @@
 # buildifier: disable=bzl-visibility
 load("//apt:defs.bzl", "dpkg_statusd")
-load("//distroless/tests:asserts.bzl", "assert_tar_listing")
+load("//distroless/tests:asserts.bzl", "assert_tar_mtree")
 
 dpkg_statusd(
     name = "statusd",
     package_name = "ca-certificates",
     control = "@example-bullseye-ca-certificates//:control.tar.xz",
 )
 
-assert_tar_listing(
+assert_tar_mtree(
     name = "test_statusd",
     actual = "statusd",
     expected = """\