Move CLC construction to Ninja phase.

Before this change, dexpreopt was often broken with optional libraries.
This was because the CLC construction was done in Soong at an early
stage, where we don't have sufficient information to determine whether
an optional library is installed or not.

For example, the "Settings" package uses an optional library called
"androidx.window.extensions". On some devices, the library is installed,
but on some other devices, it's not. Soong always adds the library to
the CLC, meaning the CLC is wrong for devices which don't have the
library. This change fixes the problem. See the tests below.

After this change, the CLC construction is done by a Python script
invoked at a very late stage. It uses product_packages.txt, which is
generated by Make, to determine whether an optional library is
installed or not, and filter out libraries that are not installed.

Note that optional libraries are still added as dependencies by Soong.
This is because dependencies have to be added at an early stage. This
means what dex2oat eventually uses will be a subset of the dependencies,
which is fine.

Bug: 282877248
Test: m
Test: atest construct_context_test
Test: -
  1. lunch aosp_cf_x86_64_phone-userdebug && m
  2. Check the .invocation file of the "Settings" package (defined in
     .bp file)
  3. See androidx.window.extensions
Test: -
  1. lunch aosp_redfin-userdebug && m
  2. Check the .invocation file of the "Settings" package (defined in
     .bp file)
  3. Don't see androidx.window.extensions
Test: Check the .invocation file of the "Dialer" package (defined in
  .mk file)
Test: -
  1. Build a Pixel 5 system image and flash it to a Pixel 5 device.
  2. adb shell pm art dump
  3. See "reason=prebuilt" instead of "reason=vdex".
     (https://diff.googleplex.com/#key=fB6Ls9q2QGSN, before: left,
     after: right)

Change-Id: Ia112bd7c2328373e68db6bffb74bf34030f683d8
diff --git a/scripts/construct_context.py b/scripts/construct_context.py
index 3f601c3..fc3a89e 100755
--- a/scripts/construct_context.py
+++ b/scripts/construct_context.py
@@ -19,6 +19,7 @@
 from __future__ import print_function
 
 import argparse
+import json
 import sys
 
 from manifest import compare_version_gt
@@ -33,20 +34,14 @@
         dest='sdk',
         help='specify target SDK version (as it appears in the manifest)')
     parser.add_argument(
-        '--host-context-for-sdk',
-        dest='host_contexts',
-        action='append',
-        nargs=2,
-        metavar=('sdk', 'context'),
-        help='specify context on host for a given SDK version or "any" version')
+        '--context-json',
+        default='',
+        dest='context_json',
+    )
     parser.add_argument(
-        '--target-context-for-sdk',
-        dest='target_contexts',
-        action='append',
-        nargs=2,
-        metavar=('sdk', 'context'),
-        help='specify context on target for a given SDK version or "any" '
-        'version'
+        '--product-packages',
+        default='',
+        dest='product_packages_file',
     )
     return parser.parse_args(args)
 
@@ -55,28 +50,69 @@
 # context regardless of the target SDK version.
 any_sdk = 'any'
 
-
-# We assume that the order of context arguments passed to this script is
-# correct (matches the order computed by package manager). It is possible to
-# sort them here, but Soong needs to use deterministic order anyway, so it can
-# as well use the correct order.
-def construct_context(versioned_contexts, target_sdk):
-    context = []
-    for [sdk, ctx] in versioned_contexts:
-        if sdk == any_sdk or compare_version_gt(sdk, target_sdk):
-            context.append(ctx)
-    return context
+context_sep = '#'
 
 
-def construct_contexts(args):
-    host_context = construct_context(args.host_contexts, args.sdk)
-    target_context = construct_context(args.target_contexts, args.sdk)
-    context_sep = '#'
+def encode_class_loader(context, product_packages):
+    host_sub_contexts, target_sub_contexts = encode_class_loaders(
+            context['Subcontexts'], product_packages)
+
+    return ('PCL[%s]%s' % (context['Host'], host_sub_contexts),
+            'PCL[%s]%s' % (context['Device'], target_sub_contexts))
+
+
+def encode_class_loaders(contexts, product_packages):
+    host_contexts = []
+    target_contexts = []
+
+    for context in contexts:
+        if not context['Optional'] or context['Name'] in product_packages:
+            host_context, target_context = encode_class_loader(
+                    context, product_packages)
+            host_contexts.append(host_context)
+            target_contexts.append(target_context)
+
+    if host_contexts:
+        return ('{%s}' % context_sep.join(host_contexts),
+                '{%s}' % context_sep.join(target_contexts))
+    else:
+        return '', ''
+
+
+def construct_context_args(target_sdk, context_json, product_packages):
+    all_contexts = []
+
+    # CLC for different SDK versions should come in specific order that agrees
+    # with PackageManager. Since PackageManager processes SDK versions in
+    # ascending order and prepends compatibility libraries at the front, the
+    # required order is descending, except for any_sdk that has numerically
+    # the largest order, but must be the last one. Example of correct order:
+    # [30, 29, 28, any_sdk]. There are Python tests to ensure that someone
+    # doesn't change this by accident, but there is no way to guard against
+    # changes in the PackageManager, except for grepping logcat on the first
+    # boot for absence of the following messages:
+    #
+    #   `logcat | grep -E 'ClassLoaderContext [a-z ]+ mismatch`
+
+    for sdk, contexts in sorted(
+            ((sdk, contexts)
+             for sdk, contexts in context_json.items()
+             if sdk != any_sdk and compare_version_gt(sdk, target_sdk)),
+            key=lambda item: int(item[0]), reverse=True):
+        all_contexts += contexts
+
+    if any_sdk in context_json:
+        all_contexts += context_json[any_sdk]
+
+    host_contexts, target_contexts = encode_class_loaders(
+            all_contexts, product_packages)
+
     return (
-        'class_loader_context_arg=--class-loader-context=PCL[]{%s} ; ' %
-        context_sep.join(host_context) +
-        'stored_class_loader_context_arg=--stored-class-loader-context=PCL[]{%s}' #pylint: disable=line-too-long
-        % context_sep.join(target_context))
+        'class_loader_context_arg=--class-loader-context=PCL[]%s ; ' %
+        host_contexts +
+        'stored_class_loader_context_arg='
+        '--stored-class-loader-context=PCL[]%s'
+        % target_contexts)
 
 
 def main():
@@ -85,12 +121,12 @@
         args = parse_args(sys.argv[1:])
         if not args.sdk:
             raise SystemExit('target sdk version is not set')
-        if not args.host_contexts:
-            args.host_contexts = []
-        if not args.target_contexts:
-            args.target_contexts = []
 
-        print(construct_contexts(args))
+        context_json = json.loads(args.context_json)
+        with open(args.product_packages_file, 'r') as f:
+            product_packages = set(line.strip() for line in f if line.strip())
+
+        print(construct_context_args(args.sdk, context_json, product_packages))
 
     # pylint: disable=broad-except
     except Exception as err:
diff --git a/scripts/construct_context_test.py b/scripts/construct_context_test.py
index 2ff5ac5..34a0e16 100755
--- a/scripts/construct_context_test.py
+++ b/scripts/construct_context_test.py
@@ -24,62 +24,249 @@
 sys.dont_write_bytecode = True
 
 
-def construct_contexts(arglist):
-    args = cc.parse_args(arglist)
-    return cc.construct_contexts(args)
+CONTEXT_JSON = {
+    '28': [
+        {
+            'Name': 'z',
+            'Optional': False,
+            'Host': 'out/zdir/z.jar',
+            'Device': '/system/z.jar',
+            'Subcontexts': [],
+        },
+    ],
+    '29': [
+        {
+            'Name': 'x',
+            'Optional': False,
+            'Host': 'out/xdir/x.jar',
+            'Device': '/system/x.jar',
+            'Subcontexts': [],
+        },
+        {
+            'Name': 'y',
+            'Optional': False,
+            'Host': 'out/ydir/y.jar',
+            'Device': '/product/y.jar',
+            'Subcontexts': [],
+        },
+    ],
+    'any': [
+        {
+            'Name': 'a',
+            'Optional': False,
+            'Host': 'out/adir/a.jar',
+            'Device': '/system/a.jar',
+            'Subcontexts': [
+                {  # Not installed optional, being the only child.
+                    'Name': 'a1',
+                    'Optional': True,
+                    'Host': 'out/a1dir/a1.jar',
+                    'Device': '/product/a1.jar',
+                    'Subcontexts': [],
+                },
+            ],
+        },
+        {
+            'Name': 'b',
+            'Optional': True,
+            'Host': 'out/bdir/b.jar',
+            'Device': '/product/b.jar',
+            'Subcontexts': [
+                {  # Not installed but required.
+                    'Name': 'b1',
+                    'Optional': False,
+                    'Host': 'out/b1dir/b1.jar',
+                    'Device': '/product/b1.jar',
+                    'Subcontexts': [],
+                },
+                {  # Installed optional.
+                    'Name': 'b2',
+                    'Optional': True,
+                    'Host': 'out/b2dir/b2.jar',
+                    'Device': '/product/b2.jar',
+                    'Subcontexts': [],
+                },
+                {  # Not installed optional.
+                    'Name': 'b3',
+                    'Optional': True,
+                    'Host': 'out/b3dir/b3.jar',
+                    'Device': '/product/b3.jar',
+                    'Subcontexts': [],
+                },
+                {  # Installed optional with one more level of nested deps.
+                    'Name': 'b4',
+                    'Optional': True,
+                    'Host': 'out/b4dir/b4.jar',
+                    'Device': '/product/b4.jar',
+                    'Subcontexts': [
+                        {
+                            'Name': 'b41',
+                            'Optional': True,
+                            'Host': 'out/b41dir/b41.jar',
+                            'Device': '/product/b41.jar',
+                            'Subcontexts': [],
+                        },
+                        {
+                            'Name': 'b42',
+                            'Optional': True,
+                            'Host': 'out/b42dir/b42.jar',
+                            'Device': '/product/b42.jar',
+                            'Subcontexts': [],
+                        },
+                    ],
+                },
+            ],
+        },
+        {  # Not installed optional, at the top-level.
+            'Name': 'c',
+            'Optional': True,
+            'Host': 'out/cdir/c.jar',
+            'Device': '/product/c.jar',
+            'Subcontexts': [],
+        },
+    ],
+}
 
 
-contexts = [
-    '--host-context-for-sdk',
-    '28',
-    'PCL[out/zdir/z.jar]',
-    '--target-context-for-sdk',
-    '28',
-    'PCL[/system/z.jar]',
-    '--host-context-for-sdk',
-    '29',
-    'PCL[out/xdir/x.jar]#PCL[out/ydir/y.jar]',
-    '--target-context-for-sdk',
-    '29',
-    'PCL[/system/x.jar]#PCL[/product/y.jar]',
-    '--host-context-for-sdk',
-    'any',
-    'PCL[out/adir/a.jar]#PCL[out/bdir/b.jar]',
-    '--target-context-for-sdk',
-    'any',
-    'PCL[/system/a.jar]#PCL[/product/b.jar]',
-]
+PRODUCT_PACKAGES = ['a', 'b', 'b2', 'b4', 'b41', 'b42', 'x', 'y', 'z']
 
-#pylint: disable=line-too-long
+
+def construct_context_args(target_sdk):
+    return cc.construct_context_args(target_sdk, CONTEXT_JSON, PRODUCT_PACKAGES)
+
+
 class ConstructContextTest(unittest.TestCase):
+    def test_construct_context_27(self):
+        actual = construct_context_args('27')
+        # The order matters.
+        expected = (
+            'class_loader_context_arg='
+            '--class-loader-context=PCL[]{'
+            'PCL[out/xdir/x.jar]#'
+            'PCL[out/ydir/y.jar]#'
+            'PCL[out/zdir/z.jar]#'
+            'PCL[out/adir/a.jar]#'
+            'PCL[out/bdir/b.jar]{'
+            'PCL[out/b1dir/b1.jar]#'
+            'PCL[out/b2dir/b2.jar]#'
+            'PCL[out/b4dir/b4.jar]{'
+            'PCL[out/b41dir/b41.jar]#'
+            'PCL[out/b42dir/b42.jar]'
+            '}'
+            '}'
+            '}'
+            ' ; '
+            'stored_class_loader_context_arg='
+            '--stored-class-loader-context=PCL[]{'
+            'PCL[/system/x.jar]#'
+            'PCL[/product/y.jar]#'
+            'PCL[/system/z.jar]#'
+            'PCL[/system/a.jar]#'
+            'PCL[/product/b.jar]{'
+            'PCL[/product/b1.jar]#'
+            'PCL[/product/b2.jar]#'
+            'PCL[/product/b4.jar]{'
+            'PCL[/product/b41.jar]#'
+            'PCL[/product/b42.jar]'
+            '}'
+            '}'
+            '}')
+        self.assertEqual(actual, expected)
 
     def test_construct_context_28(self):
-        args = ['--target-sdk-version', '28'] + contexts
-        result = construct_contexts(args)
-        expect = (
-            'class_loader_context_arg=--class-loader-context=PCL[]{PCL[out/xdir/x.jar]#PCL[out/ydir/y.jar]#PCL[out/adir/a.jar]#PCL[out/bdir/b.jar]}'
+        actual = construct_context_args('28')
+        expected = (
+            'class_loader_context_arg='
+            '--class-loader-context=PCL[]{'
+            'PCL[out/xdir/x.jar]#'
+            'PCL[out/ydir/y.jar]#'
+            'PCL[out/adir/a.jar]#'
+            'PCL[out/bdir/b.jar]{'
+            'PCL[out/b1dir/b1.jar]#'
+            'PCL[out/b2dir/b2.jar]#'
+            'PCL[out/b4dir/b4.jar]{'
+            'PCL[out/b41dir/b41.jar]#'
+            'PCL[out/b42dir/b42.jar]'
+            '}'
+            '}'
+            '}'
             ' ; '
-            'stored_class_loader_context_arg=--stored-class-loader-context=PCL[]{PCL[/system/x.jar]#PCL[/product/y.jar]#PCL[/system/a.jar]#PCL[/product/b.jar]}')
-        self.assertEqual(result, expect)
+            'stored_class_loader_context_arg='
+            '--stored-class-loader-context=PCL[]{'
+            'PCL[/system/x.jar]#'
+            'PCL[/product/y.jar]#'
+            'PCL[/system/a.jar]#'
+            'PCL[/product/b.jar]{'
+            'PCL[/product/b1.jar]#'
+            'PCL[/product/b2.jar]#'
+            'PCL[/product/b4.jar]{'
+            'PCL[/product/b41.jar]#'
+            'PCL[/product/b42.jar]'
+            '}'
+            '}'
+            '}')
+        self.assertEqual(actual, expected)
 
     def test_construct_context_29(self):
-        args = ['--target-sdk-version', '29'] + contexts
-        result = construct_contexts(args)
-        expect = (
-            'class_loader_context_arg=--class-loader-context=PCL[]{PCL[out/adir/a.jar]#PCL[out/bdir/b.jar]}'
+        actual = construct_context_args('29')
+        expected = (
+            'class_loader_context_arg='
+            '--class-loader-context=PCL[]{'
+            'PCL[out/adir/a.jar]#'
+            'PCL[out/bdir/b.jar]{'
+            'PCL[out/b1dir/b1.jar]#'
+            'PCL[out/b2dir/b2.jar]#'
+            'PCL[out/b4dir/b4.jar]{'
+            'PCL[out/b41dir/b41.jar]#'
+            'PCL[out/b42dir/b42.jar]'
+            '}'
+            '}'
+            '}'
             ' ; '
-            'stored_class_loader_context_arg=--stored-class-loader-context=PCL[]{PCL[/system/a.jar]#PCL[/product/b.jar]}')
-        self.assertEqual(result, expect)
+            'stored_class_loader_context_arg='
+            '--stored-class-loader-context=PCL[]{'
+            'PCL[/system/a.jar]#'
+            'PCL[/product/b.jar]{'
+            'PCL[/product/b1.jar]#'
+            'PCL[/product/b2.jar]#'
+            'PCL[/product/b4.jar]{'
+            'PCL[/product/b41.jar]#'
+            'PCL[/product/b42.jar]'
+            '}'
+            '}'
+            '}')
+        self.assertEqual(actual, expected)
 
     def test_construct_context_S(self):
-        args = ['--target-sdk-version', 'S'] + contexts
-        result = construct_contexts(args)
-        expect = (
-            'class_loader_context_arg=--class-loader-context=PCL[]{PCL[out/adir/a.jar]#PCL[out/bdir/b.jar]}'
+        actual = construct_context_args('S')
+        expected = (
+            'class_loader_context_arg='
+            '--class-loader-context=PCL[]{'
+            'PCL[out/adir/a.jar]#'
+            'PCL[out/bdir/b.jar]{'
+            'PCL[out/b1dir/b1.jar]#'
+            'PCL[out/b2dir/b2.jar]#'
+            'PCL[out/b4dir/b4.jar]{'
+            'PCL[out/b41dir/b41.jar]#'
+            'PCL[out/b42dir/b42.jar]'
+            '}'
+            '}'
+            '}'
             ' ; '
-            'stored_class_loader_context_arg=--stored-class-loader-context=PCL[]{PCL[/system/a.jar]#PCL[/product/b.jar]}')
-        self.assertEqual(result, expect)
-#pylint: enable=line-too-long
+            'stored_class_loader_context_arg='
+            '--stored-class-loader-context=PCL[]{'
+            'PCL[/system/a.jar]#'
+            'PCL[/product/b.jar]{'
+            'PCL[/product/b1.jar]#'
+            'PCL[/product/b2.jar]#'
+            'PCL[/product/b4.jar]{'
+            'PCL[/product/b41.jar]#'
+            'PCL[/product/b42.jar]'
+            '}'
+            '}'
+            '}')
+        self.assertEqual(actual, expected)
+
 
 if __name__ == '__main__':
     unittest.main(verbosity=2)