Fix #941: Use the right arch for foreign-arch-only packages (#943)

This is a follow-up to #935.

* fix regression #941: pmbootstrap doesn't automatically pick the
  right architecture for building when none is specified
* remove obsolete --noarch-arch parameter

pmb/build/autodetect.py

@@ -22,6 +22,22 @@ import pmb.chroot.apk
 import pmb.parse.arch
 
 
+def arch(args, pkgname):
+    """
+    Find a good default in case the user did not specify for which architecture
+    a package should be built.
+
+    :returns: native architecture (x86_64 in most cases) when the APKBUILD has
+              "noarch" or "all". Otherwise the first architecture in the
+              APKBUILD.
+    """
+    aport = pmb.build.find_aport(args, pkgname)
+    apkbuild = pmb.parse.apkbuild(args, aport + "/APKBUILD")
+    if "noarch" in apkbuild["arch"] or "all" in apkbuild["arch"]:
+        return args.arch_native
+    return apkbuild["arch"][0]
+
+
 def suffix(args, apkbuild, arch):
     if arch == args.arch_native:
         return "native"

pmb/helpers/frontend.py

@@ -27,6 +27,7 @@ import sys
 
 import pmb.aportgen
 import pmb.build
+import pmb.build.autodetect
 import pmb.config
 import pmb.challenge
 import pmb.chroot
@@ -141,7 +142,8 @@ def build(args):
 
     # Build all packages
     for package in args.packages:
-        pmb.build.package(args, package, args.arch, args.force,
+        arch_package = args.arch or pmb.build.autodetect.arch(args, package)
+        pmb.build.package(args, package, arch_package, args.force,
                           args.buildinfo, args.strict)
 
 

pmb/parse/apkbuild.py

@@ -156,6 +156,10 @@ def apkbuild(args, path):
         raise RuntimeError("The pkgname must be equal to the name of"
                            " the folder, that contains the APKBUILD!")
 
+    # Sanity check: arch
+    if not len(ret["arch"]):
+        raise RuntimeError("Arch must not be empty: " + path)
+
     # Fill cache
     args.cache["apkbuild"][path] = ret
     return ret

pmb/parse/arguments.py

@@ -270,9 +270,10 @@ def arguments():
                               " (aport/APKBUILD) based on an upstream aport from Alpine")
     build = sub.add_parser("build", help="create a package for a"
                            " specific architecture")
-    build.add_argument("--arch", choices=arch_choices, default=arch_native,
+    build.add_argument("--arch", choices=arch_choices, default=None,
                        help="CPU architecture to build for (default: " +
-                       arch_native + ")")
+                       arch_native + " or first available architecture in"
+                       " APKBUILD)")
     build.add_argument("--force", action="store_true", help="even build if not"
                        " necessary")
     build.add_argument("--buildinfo", action="store_true")
@@ -285,13 +286,6 @@ def arguments():
                        " you don't need to build and install the kernel. But it"
                        " is incompatible with how Alpine's abuild handles it.",
                        dest="ignore_depends")
-    build.add_argument("--noarch-arch", dest="noarch_arch", default=None,
-                       help="which architecture to use to build 'noarch'"
-                            " packages. Defaults to the native arch normally,"
-                            " and to the device arch when --strict is set."
-                            " Override in case of strict mode failing on"
-                            " dependencies, which only exist for a certain"
-                            " arch.")
     for action in [checksum, build, aportgen]:
         action.add_argument("packages", nargs="+")