Introduction of a friendly user setup checker.

This patch fixes #274.

Indeed, before this patch, there was no was to send some message to the
user when some common setup mistakes were found.
This patch fixes it by adding a "message collector" that is later printed
the end user.

For now on, the configuration checker only checks against #274, but this
patch opens the door for other improvement in the future.

Contributors:
  * @ZeroDot1
  * @spirillen

Author: funilrys

PyFunceble/cli/storage.py

@@ -52,7 +52,7 @@
 
 import os
 import sys
-from typing import Optional
+from typing import List, Optional
 
 import colorama
 from box import Box
@@ -213,3 +213,6 @@
     PyFunceble.cli.storage_facility.get_output_directory(),
     OUTPUTS.parent_directory,
 )
+
+# This one will store some extra messages to print to the user.
+EXTRA_MESSAGES: Optional[List[str]] = []

PyFunceble/cli/system/integrator.py

@@ -53,6 +53,8 @@
 
 import os
 
+import colorama
+
 import PyFunceble.cli.facility
 import PyFunceble.cli.factory
 import PyFunceble.cli.storage
@@ -151,6 +153,30 @@ def inject_into_config(self) -> "SystemIntegrator":
 
         return self
 
+    @SystemBase.ensure_args_is_given
+    def check_config(self) -> "SystemIntegrator":
+        """
+        Checks or do some sanity check of the configuration.
+
+        This method will basically check that the common mistakes while mixing
+        configuration and CLI arguments are not found.
+
+        .. warning::
+            The messages are not directly printed, but rather stored in the
+            PyFunceble.cli.storage.EXTRA_MESSAGES list.
+        """
+
+        if (
+            not PyFunceble.storage.CONFIGURATION.cli_testing.file_generation.hosts
+            and not PyFunceble.storage.CONFIGURATION.cli_testing.file_generation.plain
+        ):
+            PyFunceble.cli.storage.EXTRA_MESSAGES.append(
+                f"{colorama.Style.BRIGHT}{colorama.Fore.MAGENTA}Your setup won't "
+                "generate any output! "
+                "Reason: file_generation.hosts and file_generation.plain are "
+                "both disabled."
+            )
+
     @SystemBase.ensure_args_is_given
     def start(self) -> "SystemIntegrator":
         """
@@ -170,6 +196,7 @@ def start(self) -> "SystemIntegrator":
         PyFunceble.facility.Logger.debug("Given arguments:\n%r", self.args)
 
         self.inject_into_config()
+        self.check_config()
 
         PyFunceble.cli.facility.CredentialLoader.start()
         PyFunceble.cli.factory.DBSession.init_db_sessions()

PyFunceble/cli/utils/version.py

@@ -60,6 +60,7 @@
 import PyFunceble.cli.storage
 import PyFunceble.facility
 import PyFunceble.storage
+from PyFunceble.cli.utils.stdout import print_single_line
 from PyFunceble.converter.internal_url import InternalUrlConverter
 from PyFunceble.helpers.dict import DictHelper
 from PyFunceble.helpers.download import DownloadHelper
@@ -340,7 +341,7 @@ def handle_messages(upstream_version: Box) -> None:
 
 def print_central_messages(check_force_update: bool = False) -> None:
     """
-    Compares the version with the upstream one and handle the messages.
+    Collect all possible messages from upstream and downstream and print them.
     """
 
     upstream_version = get_upstream_version()
@@ -355,3 +356,6 @@ def print_central_messages(check_force_update: bool = False) -> None:
     )
 
     handle_messages(upstream_version)
+
+    for extra_message in PyFunceble.cli.storage.EXTRA_MESSAGES:
+        print_single_line(extra_message, force=True)