BUILD_BROKEN_DUP_SYSPROP as escape hatch for the new sysprop restriction am: 0b4fccb6

# Build System Changes for Android.mk Writers

## Changes in system properties settings

### Product variables

System properties for each of the partition is supposed to be set via following

product config variables.

For system partititon,

* `PRODUCT_SYSTEM_PROPERITES`

* `PRODUCT_SYSTEM_DEFAULT_PROPERTIES` is highly discouraged. Will be deprecated.

For vendor partition,

* `PRODUCT_VENDOR_PROPERTIES`

* `PRODUCT_PROPERTY_OVERRIDES` is highly discouraged. Will be deprecated.

* `PRODUCT_DEFAULT_PROPERTY_OVERRIDES` is also discouraged. Will be deprecated.

For odm partition,

* `PRODUCT_ODM_PROPERTIES`

For system_ext partition,

* `PRODUCT_SYSTEM_EXT_PROPERTIES`

For product partition,

* `PRODUCT_PRODUCT_PROPERTIES`

### Duplication is not allowed within a partition

For each partition, having multiple sysprop assignments for the same name is

prohibited. For example, the following will now trigger an error:

`PRODUCT_VENDOR_PROPERTIES += foo=true foo=false`

Having duplication across partitions are still allowed. So, the following is

not an error:

`PRODUCT_VENDOR_PROPERTIES += foo=true`

`PRODUCT_SYSTEM_PROPERTIES += foo=false`

In that case, the final value is determined at runtime. The precedence is

* product

* odm

* vendor

* system_ext

* system

So, `foo` becomes `true` because vendor has higher priority than system.

To temporarily turn the build-time restriction off, use

`BUILD_BROKEN_DUP_SYSPROP := true`

### Optional assignments

System properties can now be set as optional using the new syntax:

`name ?= value`

Then the system property named `name` gets the value `value` only when there

is no other non-optional assignments having the same name. For example, the

following is allowed and `foo` gets `true`

`PRODUCT_VENDOR_PROPERTIES += foo=true foo?=false`

Note that the order between the optional and the non-optional assignments

doesn't matter. The following gives the same result as above.

`PRODUCT_VENDOR_PROPERTIES += foo?=false foo=true`

Optional assignments can be duplicated and in that case their order matters.

Specifically, the last one eclipses others.

`PRODUCT_VENDOR_PROPERTIES += foo?=apple foo?=banana foo?=mango`

With above, `foo` becomes `mango` since its the last one.

Note that this behavior is different from the previous behavior of preferring

the first one. To go back to the original behavior for compatability reason,

use:

`BUILD_BROKEN_DUP_SYSPROP := true`

## ELF prebuilts in PRODUCT_COPY_FILES

ELF prebuilts in PRODUCT_COPY_FILES that are installed into these paths are an

  BUILD_BROKEN_TREBLE_SYSPROP_NEVERALLOW \

  BUILD_BROKEN_USES_NETWORK \

  BUILD_BROKEN_VINTF_PRODUCT_COPY_FILES \

  BUILD_BROKEN_DUP_SYSPROP \

_build_broken_var_list += \

  $(foreach m,$(AVAILABLE_BUILD_MODULE_TYPES) \

    $(eval _resolved_$(name) := $$(call collapse-pairs,$$(_temp),=))\

)

$(eval # Implement the legacy behavior when BUILD_BROKEN_DUP_SYSPROP is on.)

$(eval # Optional assignments are all converted to normal assignments and)

$(eval # when their duplicates the first one wins)

$(if $(filter true,$(BUILD_BROKEN_DUP_SYSPROP)),\

    $(foreach name,$(strip $(4)),\

        $(eval _temp := $$(subst ?=,=,$$(_resolved_$(name))))\

        $(eval _resolved_$(name) := $$(call uniq-pairs-by-first-component,$$(_resolved_$(name)),=))\

    )\

    $(eval _option := --allow-dup)\

)

$(2): $(POST_PROCESS_PROPS) $(INTERNAL_BUILD_ID_MAKEFILE) $(API_FINGERPRINT) $(3)

	$(hide) echo Building $$@

	$(hide) mkdir -p $$(dir $$@)

	        echo "$$(line)" >> $$@;\

	    )\

	)

	$(hide) $(POST_PROCESS_PROPS) $$@ $(5)

	$(hide) $(POST_PROCESS_PROPS) $$(_option) $$@ $(5)

	$(hide) echo "# end of file" >> $$@

endef

# See the License for the specific language governing permissions and

# limitations under the License.

import argparse

import sys

# Usage: post_process_props.py file.prop [disallowed_key, ...]

  return check_pass

def override_optional_props(prop_list):

def override_optional_props(prop_list, allow_dup=False):

  """Override a?=b with a=c, if the latter exists

  Overriding is done by deleting a?=b

      # duplicated props are allowed when the all have the same value

      if all(overriding_props[0].value == p.value for p in overriding_props):

        continue

      # or if dup is explicitly allowed for compat reason

      if allow_dup:

        # this could left one or more optional props unresolved.

        # Convert them into non-optional because init doesn't understand ?=

        # syntax

        for p in optional_props:

          p.optional = False

        continue

      success = False

      sys.stderr.write("error: found duplicate sysprop assignments:\n")

      for p in overriding_props:

        f.write(str(p) + "\n")

def main(argv):

  filename = argv[1]

  if not filename.endswith("/build.prop"):

  parser = argparse.ArgumentParser(description="Post-process build.prop file")

  parser.add_argument("--allow-dup", dest="allow_dup", action="store_true",

                      default=False)

  parser.add_argument("filename")

  parser.add_argument("disallowed_keys", metavar="KEY", type=str, nargs="*")

  args = parser.parse_args()

  if not args.filename.endswith("/build.prop"):

    sys.stderr.write("bad command line: " + str(argv) + "\n")

    sys.exit(1)

  props = PropList(filename)

  props = PropList(args.filename)

  mangle_build_prop(props)

  if not override_optional_props(props):

  if not override_optional_props(props, args.allow_dup):

    sys.exit(1)

  if not validate(props):

    sys.exit(1)

  # Drop any disallowed keys

  for key in argv[2:]:

  for key in args.disallowed_keys:

    for p in props.get_props(key):

      p.delete("%s is a disallowed key" % key)

  props.write(filename)

  props.write(args.filename)

if __name__ == "__main__":

  main(sys.argv)

        # since they have the same value

        self.assertTrue(override_optional_props(props))

  def test_allowDuplicates(self):

    content = """

    # comment

    foo=true

    bar=false

    qux?=1

    foo=false

    # another comment

    foo?=false

    """

    with patch("post_process_props.open", mock_open(read_data=content)) as m:

      stderr_redirect = io.StringIO()

      with contextlib.redirect_stderr(stderr_redirect):

        props = PropList("hello")

        # we have duplicated foo=true and foo=false, but that's allowed

        # because it's explicitly allowed

        self.assertTrue(override_optional_props(props, allow_dup=True))

if __name__ == '__main__':

    unittest.main(verbosity=2)