Added missing recommendations command and cleaned up code (#1975)

* Added missing recommendations command and cleaned up code

* Added test for print_recommendations running correctly

* Updated minimum Python version to 3.6

This should have been the original value, agreed in
#1918

* Added a blank line to make pylint happy

* Moved f-strings to format calls to preserve py2 compat in this file

* Changed travis build to use Python 3.8

* Undid travis change, for merging in a separate PR

pythonforandroid/recommendations.py

@@ -11,37 +11,39 @@
 MIN_NDK_VERSION = 19
 MAX_NDK_VERSION = 20
 
+# DO NOT CHANGE LINE FORMAT: buildozer parses the existence of a RECOMMENDED_NDK_VERSION
 RECOMMENDED_NDK_VERSION = "19b"
+
 NDK_DOWNLOAD_URL = "https://developer.android.com/ndk/downloads/"
 
 # Important log messages
 NEW_NDK_MESSAGE = 'Newer NDKs may not be fully supported by p4a.'
 UNKNOWN_NDK_MESSAGE = (
-    'Could not determine NDK version, no source.properties in the NDK dir'
+    'Could not determine NDK version, no source.properties in the NDK dir.'
 )
 PARSE_ERROR_NDK_MESSAGE = (
-    'Could not parse $NDK_DIR/source.properties, not checking NDK version'
+    'Could not parse $NDK_DIR/source.properties, not checking NDK version.'
 )
 READ_ERROR_NDK_MESSAGE = (
-    'Unable to read the NDK version from the given directory {ndk_dir}'
+    'Unable to read the NDK version from the given directory {ndk_dir}.'
 )
 ENSURE_RIGHT_NDK_MESSAGE = (
     'Make sure your NDK version is greater than {min_supported}. If you get '
-    'build errors, download the recommended NDK {rec_version} from {ndk_url}'
+    'build errors, download the recommended NDK {rec_version} from {ndk_url}.'
 )
 NDK_LOWER_THAN_SUPPORTED_MESSAGE = (
     'The minimum supported NDK version is {min_supported}. '
-    'You can download it from {ndk_url}'
+    'You can download it from {ndk_url}.'
 )
 UNSUPPORTED_NDK_API_FOR_ARMEABI_MESSAGE = (
     'Asked to build for armeabi architecture with API '
-    '{req_ndk_api}, but API {max_ndk_api} or greater does not support armeabi'
+    '{req_ndk_api}, but API {max_ndk_api} or greater does not support armeabi.'
 )
 CURRENT_NDK_VERSION_MESSAGE = (
     'Found NDK version {ndk_version}'
 )
 RECOMMENDED_NDK_VERSION_MESSAGE = (
-    'Maximum recommended NDK version is {recommended_ndk_version}'
+    'Maximum recommended NDK version is {recommended_ndk_version}, but newer versions may work.'
 )
 
 
@@ -187,7 +189,7 @@ def check_ndk_api(ndk_api, android_api):
 
 
 MIN_PYTHON_MAJOR_VERSION = 3
-MIN_PYTHON_MINOR_VERSION = 4
+MIN_PYTHON_MINOR_VERSION = 6
 MIN_PYTHON_VERSION = LooseVersion('{major}.{minor}'.format(major=MIN_PYTHON_MAJOR_VERSION,
                                                            minor=MIN_PYTHON_MINOR_VERSION))
 PY2_ERROR_TEXT = (
@@ -218,3 +220,15 @@ def check_python_version():
     ):
 
         raise BuildInterruptingException(PY_VERSION_ERROR_TEXT)
+
+
+def print_recommendations():
+    """
+    Print the main recommended dependency versions as simple key-value pairs.
+    """
+    print('Min supported NDK version: {}'.format(MIN_NDK_VERSION))
+    print('Recommended NDK version: {}'.format(RECOMMENDED_NDK_VERSION))
+    print('Min target API: {}'.format(MIN_TARGET_API))
+    print('Recommended target API: {}'.format(RECOMMENDED_TARGET_API))
+    print('Min NDK API: {}'.format(MIN_NDK_API))
+    print('Recommended NDK API: {}'.format(RECOMMENDED_NDK_API))

pythonforandroid/toolchain.py

@@ -11,7 +11,7 @@
 from pythonforandroid import __version__
 from pythonforandroid.pythonpackage import get_dep_names_of_package
 from pythonforandroid.recommendations import (
-    RECOMMENDED_NDK_API, RECOMMENDED_TARGET_API)
+    RECOMMENDED_NDK_API, RECOMMENDED_TARGET_API, print_recommendations)
 from pythonforandroid.util import BuildInterruptingException
 from pythonforandroid.entrypoints import main
 
@@ -1163,6 +1163,9 @@ def _adb(self, commands):
             sys.stdout.write(line)
             sys.stdout.flush()
 
+    def recommendations(self, args):
+        print_recommendations()
+
     def build_status(self, _args):
         """Print the status of the specified build. """
         print('{Style.BRIGHT}Bootstraps whose core components are probably '

tests/test_recommendations.py

@@ -9,6 +9,7 @@
     check_target_api,
     read_ndk_version,
     check_python_version,
+    print_recommendations,
     MAX_NDK_VERSION,
     RECOMMENDED_NDK_VERSION,
     RECOMMENDED_TARGET_API,
@@ -237,3 +238,12 @@ def test_check_python_version(self):
             fake_version_info.major = MIN_PYTHON_MAJOR_VERSION
             fake_version_info.minor = MIN_PYTHON_MINOR_VERSION
             check_python_version()
+
+    def test_print_recommendations(self):
+        """
+        Simple test that the function actually runs.
+        """
+        # The main failure mode is if the function tries to print a variable
+        # that doesn't actually exist, so simply running to check all the
+        # prints work is the most important test.
+        print_recommendations()