mmdebstrap and sbuild shall agree on what build_path means

While mmdebstrap would extract the package precisely to the build_path,
sbuild would create a subdirectory <source>-<upstream_version> inside
the build_path. Changing sbuild to do the mmdebstrap behaviour looks
next to impossible, so this commit changes mmdebstrap to behave like
sbuild.

pbuilder also allows changing the build_path in principle. The
documented BUILDDIR variable works quite similar to the sbuild option
--build-path. pbuilder also allows changing the sub directory using the
undocumented BUILDSUBDIR variable. That's another reason to do it like
sbuild.

3 files changed, 48 insertions, 36 deletions

diff --git a/mdbp/build_schema.json b/mdbp/build_schema.json
index 0f7e9bc..e083654 100644
--- a/mdbp/build_schema.json
+++ b/mdbp/build_schema.json
@@ -112,7 +112,7 @@
     },
     "build_path": {
       "type": "string",
-      "description": "the path inside the chroot to peform the build"
+      "description": "Specify the path inside the chroot to peform the build. This excludes the final directory dpkg-source extracts to."
     },
     "lintian": {
       "type": "object",
diff --git a/mdbp/common.py b/mdbp/common.py
index 719a8b6..5c67f58 100644
--- a/mdbp/common.py
+++ b/mdbp/common.py
@@ -118,6 +118,11 @@ def download(uri: str, checksums: typing.Dict[str, str],
             dest.unlink()
             raise
 
+def parse_dsc(dscpath: pathlib.Path) -> debian.deb822.Dsc:
+    """Parse a dsc file."""
+    with dscpath.open("r") as dscf:
+        return debian.deb822.Dsc(dscf)
+
 def download_dsc(buildinput: JsonObject,
                  destdir: pathlib.Path) -> pathlib.Path:
     """Download the .input.source_package_url including referenced components
@@ -130,12 +135,11 @@ def download_dsc(buildinput: JsonObject,
     assert isinstance(dscpath, pathlib.Path)
     download(dscuri, buildinput.get("checksums", {}), dscpath)
     files: typing.Dict[str, typing.Dict[str, str]] = {}
-    with dscpath.open("r") as dscf:
-        for key, value in debian.deb822.Dsc(dscf).items():
-            if key.lower().startswith("checksums-"):
-                for entry in value:
-                    algo = key[10:].lower()
-                    files.setdefault(entry["name"], dict())[algo] = entry[algo]
+    for key, value in parse_dsc(dscpath).items():
+        if key.lower().startswith("checksums-"):
+            for entry in value:
+                algo = key[10:].lower()
+                files.setdefault(entry["name"], dict())[algo] = entry[algo]
     for name, checksums in files.items():
         download(urllib.parse.urljoin(dscuri, name), checksums, destdir / name)
     return dscpath
@@ -155,11 +159,12 @@ def get_dsc(build: JsonObject) -> typing.Iterator[pathlib.Path]:
     else:
         yield pathlib.Path(dscpath)
 
-def get_dsc_files(dscpath: pathlib.Path) -> typing.List[pathlib.Path]:
-    """Get the component names referenced by the .dsc file."""
-    with dscpath.open("r") as dscf:
-        dsc = debian.deb822.Dsc(dscf)
-    return [dscpath.parent / item["name"] for item in dsc["Files"]]
+def get_dsc_files(dscpath: pathlib.Path,
+                  dscobj: typing.Optional[debian.deb822.Dsc] = None) -> \
+        typing.List[pathlib.Path]:
+    """Get the component names referenced by the .dsc."""
+    return [dscpath.parent / item["name"]
+            for item in (dscobj or parse_dsc(dscpath))["Files"]]
 
 def make_option(optname: str, value: typing.Optional[str]) -> typing.List[str]:
     """Construct a valued option if a value is given."""
diff --git a/mdbp/mmdebstrap.py b/mdbp/mmdebstrap.py
index c864bce..9858b65 100644
--- a/mdbp/mmdebstrap.py
+++ b/mdbp/mmdebstrap.py
@@ -16,8 +16,10 @@ import subprocess
 import sys
 import typing
 
+import debian.debian_support
+
 from .common import buildjson, clean_dir, compute_env, download_dsc, \
-        get_dsc_files, json_load, profile_option
+        get_dsc_files, json_load, parse_dsc, profile_option
 
 libc = ctypes.CDLL(ctypes.util.find_library("c"))
 def unshare_network() -> None:
@@ -59,19 +61,25 @@ def native_architecture() -> str:
     return subprocess.check_output(["dpkg", "--print-architecture"],
                                    encoding="ascii").strip()
 
+def build_subdir(dsc: debian.deb822.Dsc) -> str:
+    """Compute the subdirectory that dpkg-source normally extracts to."""
+    ver = debian.debian_support.BaseVersion(dsc["Version"]).upstream_version
+    assert ver is not None  # please mypy
+    return "%s-%s" % (dsc["Source"], ver)
+
 def hook_main(buildjsonfilename: str, chrootname: str) -> None:
     """The entry point for the --hook-helper invocation run from mmdebstrap."""
     build = json_load(pathlib.Path(buildjsonfilename).open("r"))
     chroot = pathlib.Path(chrootname)
-    buildpath = pathlib.PurePath(build.get("build_path", "/build/build"))
-    fullbuildpath = chroot / buildpath.relative_to("/")
+    builddir = pathlib.PurePath(build.get("build_path", "/build"))
+    fullbuilddir = chroot / builddir.relative_to("/")
     if "source_package_path" in build["input"]:
-        dscpath = fullbuildpath.parent / \
+        dscpath = fullbuilddir / \
                 pathlib.PurePath(build["input"]["source_package_path"]).name
     elif "source_package_url" in build["input"]:
-        dscpath = download_dsc(build["input"], fullbuildpath.parent)
+        dscpath = download_dsc(build["input"], fullbuilddir)
     priv_drop(["chown", "-R", "build:build", "."],
-               chroot=chroot, chdir=buildpath.parent)
+              chroot=chroot, chdir=builddir)
     apt_get = ["apt-get", "--yes", "-oAPT::Keep-Downloaded-Packages=false"]
     if "sourcename" in build["input"]:
         sourcename = build["input"]["sourcename"]
@@ -79,13 +87,13 @@ def hook_main(buildjsonfilename: str, chrootname: str) -> None:
             sourcename += "=" + build["input"]["version"]
         priv_drop([*apt_get, "--only-source", "--download-only", "source",
                    sourcename],
-                  chroot=chroot, chdir=buildpath.parent, setuid="build")
-        [dscpath] = fullbuildpath.parent.glob(build["input"]["sourcename"] +
-                                              "_*.dsc")
-    priv_drop(["dpkg-source", "--no-check", "--extract", dscpath.name,
-               buildpath.name],
-              setuid="build", chroot=chroot, chdir=buildpath.parent)
-    for path in [*get_dsc_files(dscpath), dscpath]:
+                  chroot=chroot, chdir=builddir, setuid="build")
+        [dscpath] = fullbuilddir.glob(build["input"]["sourcename"] + "_*.dsc")
+    dsc = parse_dsc(dscpath)
+    subdir = build_subdir(dsc)
+    priv_drop(["dpkg-source", "--no-check", "--extract", dscpath.name, subdir],
+              setuid="build", chroot=chroot, chdir=builddir)
+    for path in [*get_dsc_files(dscpath, dsc), dscpath]:
         path.unlink()
     hostarch = build.get("host_architecture") or \
             build.get("build_architecture") or \
@@ -96,7 +104,7 @@ def hook_main(buildjsonfilename: str, chrootname: str) -> None:
            *profile_option(build, "--build-profiles"),
            "./"]
     try:
-        priv_drop(cmd, chroot=chroot, chdir=buildpath)
+        priv_drop(cmd, chroot=chroot, chdir=builddir / subdir)
     except subprocess.CalledProcessError:
         if build.get("bd-uninstallable-explainer") != "apt" or \
            not build["output"].get("log", True):
@@ -105,20 +113,20 @@ def hook_main(buildjsonfilename: str, chrootname: str) -> None:
                       '-oDebug::pkgDepCache::Marker=1',
                       '-oDebug::pkgDepCache::AutoInstall=1',
                       '-oDebug::BuildDeps=1']
-        priv_drop(cmd, chroot=chroot, chdir=buildpath)
+        priv_drop(cmd, chroot=chroot, chdir=builddir / subdir)
     priv_drop(["dpkg-buildpackage", "-uc", "--host-arch=" + hostarch,
                "--build=" + build.get("type", "binary"),
                *profile_option(build, "--build-profiles=")],
               chroot=chroot, setuid="build",
               privnet=not build.get("network") in ("enable", "try-enable"),
-              chdir=buildpath, env=compute_env(build))
-    shutil.rmtree(fullbuildpath)
+              chdir=builddir / subdir, env=compute_env(build))
+    shutil.rmtree(fullbuilddir / subdir)
     if build.get("lintian", {}).get("run"):
         priv_drop([*apt_get, "install", "lintian"], chroot=chroot)
         priv_drop(["lintian", *build["lintian"].get("options", ()),
                    "%s_%s.changes" % (dscpath.stem, hostarch)],
-                  chroot=chroot, setuid="build", chdir=buildpath.parent)
-    clean_dir(fullbuildpath.parent, build["output"].get("artifacts", ["*"]))
+                  chroot=chroot, setuid="build", chdir=builddir)
+    clean_dir(fullbuilddir, build["output"].get("artifacts", ["*"]))
 
 class RawStoreAction(argparse.Action):
     """An action that stores the raw value in addition to the type-parsed
@@ -168,7 +176,7 @@ def main() -> None:
                               "libc-dev:" + hostarch,
                               "libstdc++-dev:" + hostarch,
                               "fakeroot"))
-    buildpath = pathlib.PurePath(build.get("build_path", "/build/build"))
+    builddir = build.get("build_path", "/build")
     enablelog = build["output"].get("log", True)
 
     cmd = [
@@ -182,18 +190,17 @@ def main() -> None:
         '--essential-hook=echo man-db man-db/auto-update boolean false | ' \
             'chroot "$1" debconf-set-selections',
         '--customize-hook=chroot "$1" useradd --user-group --create-home '
-            '--home-dir %s build --skel /nonexistent' %
-            shlex.quote(str(buildpath.parent)),
+            '--home-dir %s build --skel /nonexistent' % shlex.quote(builddir),
         *(["--customize-hook=copy-in " + shlex.join([
             build["input"]["source_package_path"],
             *map(str, get_dsc_files(pathlib.Path(
                     build["input"]["source_package_path"]))),
-            str(buildpath.parent)])]
+            builddir])]
           if "source_package_path" in build["input"] else ()),
         '--customize-hook=mdbp-mmdebstrap --hook-helper %s "$1"' %
             shlex.quote(args.raw_buildjson),
         *(["--customize-hook=sync-out " +
-            shlex.join([str(buildpath.parent), build["output"]["directory"]])]
+            shlex.join([builddir, build["output"]["directory"]])]
           if build["output"].get("artifacts", ["*"]) else ()),
         build["distribution"],
         "/dev/null",