Support external native executables

demo/app/build.gradle

@@ -52,7 +52,8 @@ android {
 
             // Python unit tests
             pip {
-                install "murmurhash==0.28.0"  // Requires chaquopy-libcxx
+                install "chaquopy-flac==1.3.3"
+                install "murmurhash==0.28.0"
             }
             staticProxy("chaquopy.test.static_proxy.basic", "chaquopy.test.static_proxy.header",
                         "chaquopy.test.static_proxy.method")

product/runtime/src/main/python/java/android/importer.py

@@ -22,7 +22,7 @@
 from zipimport import zipimporter
 
 import java.chaquopy
-from java._vendor.elftools.elf.elffile import ELFFile
+from java._vendor.elftools.elf.elffile import ELFError, ELFFile
 from java.chaquopy_android import AssetFile
 
 from android.os import Build
@@ -71,12 +71,33 @@ def hook(path):
                not any(finder.exists(f"{name}/__init__{suffix}") for suffix in LOADERS):
                 finder.extract_dir(name)
 
+        # Extract executables.
+        if finder.isdir("chaquopy/bin"):
+            for name in finder.listdir("chaquopy/bin"):
+                # If chaquopy/ is a Python package, it won't have been extracted above.
+                filename = finder.extract_if_changed(f"chaquopy/bin/{name}")
+                os.chmod(filename, 0o755)
+                try:
+                    finder.extract_needed(filename)
+                except ELFError:
+                    pass  # Maybe it's a shell script or something.
+
+            prepend_path("PATH", f"{finder.path}/chaquopy/bin")
+            prepend_path("LD_LIBRARY_PATH", f"{finder.path}/chaquopy/lib")
+
         # We do this here instead of in AssetFinder.__init__ because code in the .pth files may
         # require the finder to be fully available to the system, which isn't the case until
         # get_importer returns.
         site.addsitedir(finder.extract_root)
 
 
+def prepend_path(variable, path):
+    old_path = os.environ.get(variable)
+    if old_path:
+        path += ":" + old_path
+    os.environ[variable] = path
+
+
 def initialize_ctypes():
     import ctypes.util
     import sysconfig

product/runtime/src/test/python/chaquopy/test/test_android.py

@@ -24,7 +24,8 @@
 # Flags from PEP 3149.
 ABI_FLAGS = ""
 
-REQUIREMENTS = ["chaquopy-libcxx", "murmurhash", "Pygments"]
+REQUIREMENTS = ["chaquopy-libcxx", "chaquopy-flac", "chaquopy-libogg",
+                "murmurhash", "Pygments"]
 
 try:
     from android.os import Build
@@ -164,6 +165,24 @@ def test_so(self):
         # Library extraction caused by importing a Python module linked against it.
         self.check_extract_if_changed(mod, LIBCXX_FILENAME)
 
+    def test_bin(self):
+        chaquopy_dir = asset_path(REQS_ABI_ZIP, "chaquopy")
+        self.assertCountEqual(["bin", "lib"], os.listdir(chaquopy_dir))
+
+        # Execution of flac is covered by test_subprocess.
+        self.assertCountEqual(["flac", "metaflac"], os.listdir(f"{chaquopy_dir}/bin"))
+
+        # Library extraction caused by executables in chaquopy/bin. Notes:
+        #   * libFLAC and libogg are needed by the flac executable.
+        #   * libFLAC++ isn't needed by any executable, so it shouldn't exist at this point.
+        #     However, its presence in the APK is checked by test_ctypes.
+        #   * libc++_shared may exist if the tests have been run before.
+        actual = os.listdir(f"{chaquopy_dir}/lib")
+        expected = ["libFLAC.so", "libogg.so"]
+        if len(actual) > len(expected):
+            expected.append("libc++_shared.so")
+        self.assertCountEqual(expected, actual)
+
     def test_non_package_data(self):
         for dir_name, dir_description in [("", "root"), ("non_package_data", "directory"),
                                           ("non_package_data/subdir", "subdirectory")]:
@@ -774,11 +793,14 @@ def test_ctypes(self):
 
         # Library extraction caused by find_library.
         os.remove(LIBCXX_FILENAME)
-        find_library_result = find_library("c++_shared")
+        find_library_result = find_library("FLAC++")
         self.assertIsInstance(find_library_result, str)
         if platform.architecture()[0] == "32bit" or Build.VERSION.SDK_INT >= 23:
             self.assertRegex(find_library_result, r"^/")
+        libflacxx_filename = asset_path(REQS_ABI_ZIP, "chaquopy/lib/libFLAC++.so")
+        self.assertPredicate(exists, libflacxx_filename)
         self.assertPredicate(exists, LIBCXX_FILENAME)
+        os.remove(libflacxx_filename)  # Clean up for test_bin.
 
         # Work around double-underscore mangling of __android_log_write.
         def assertHasSymbol(dll, name):
@@ -915,9 +937,14 @@ def test_ssl(self):
         self.assertRegex(resp.info()["Content-type"], r"^text/html")
 
     def test_subprocess(self):
-        # An executable on the PATH.
+        # A system executable.
         subprocess.run(["ls", os.environ["HOME"]])
 
+        # An executable in the requirements.
+        self.assertEqual("flac 1.3.3\n",
+                         subprocess.run(["flac", "--version"], capture_output=True, text=True)
+                         .stdout)
+
         # A nonexistent executable.
         for name in ["nonexistent",                 # PATH search
                      "/system/bin/nonexistent"]:    # Absolute filename