From ea276fbe73fe3c7c16e2fad8d2a9eadb026657d9 Mon Sep 17 00:00:00 2001
From: Thomas Citharel <tcit@tcit.fr>
Date: Mon, 8 Nov 2021 12:14:13 +0100
Subject: [PATCH] Detect if Python3 is installed before launching PythonPort
 Genserver

Signed-off-by: Thomas Citharel <tcit@tcit.fr>
---
 lib/mobilizon.ex                       |  8 +++++++-
 lib/service/export/participants/ods.ex |  6 ++----
 lib/service/export/participants/pdf.ex |  6 ++----
 lib/service/python_port.ex             | 22 +++++++++++++++++++---
 4 files changed, 30 insertions(+), 12 deletions(-)

diff --git a/lib/mobilizon.ex b/lib/mobilizon.ex
index 95fdc27cf..608bb4c2c 100644
--- a/lib/mobilizon.ex
+++ b/lib/mobilizon.ex
@@ -51,7 +51,6 @@ defmodule Mobilizon do
         # workers
         Guardian.DB.Token.SweeperServer,
         ActivityPub.Federator,
-        Mobilizon.PythonWorker,
         TzWorld.Backend.DetsWithIndexCache,
         cachex_spec(:feed, 2500, 60, 60, &Feed.create_cache/1),
         cachex_spec(:ics, 2500, 60, 60, &ICalendar.create_cache/1),
@@ -73,6 +72,13 @@ defmodule Mobilizon do
       ] ++
         task_children(@env)
 
+    children =
+      if Mobilizon.PythonPort.python_exists?() do
+        children ++ [Mobilizon.PythonWorker]
+      else
+        children
+      end
+
     ErrorReporting.configure()
 
     # Only attach the telemetry logger when we aren't in an IEx shell
diff --git a/lib/service/export/participants/ods.ex b/lib/service/export/participants/ods.ex
index bf5299cae..e6eb6c4c9 100644
--- a/lib/service/export/participants/ods.ex
+++ b/lib/service/export/participants/ods.ex
@@ -3,10 +3,8 @@ defmodule Mobilizon.Service.Export.Participants.ODS do
   Export a list of participants to ODS
   """
 
-  alias Mobilizon.Events
+  alias Mobilizon.{Events, Export, PythonPort, PythonWorker}
   alias Mobilizon.Events.Event
-  alias Mobilizon.Export
-  alias Mobilizon.PythonWorker
   alias Mobilizon.Storage.Repo
   alias Mobilizon.Web.Gettext, as: GettextBackend
   import Mobilizon.Web.Gettext, only: [gettext: 2]
@@ -91,7 +89,7 @@ defmodule Mobilizon.Service.Export.Participants.ODS do
 
   @spec dependencies_ok? :: boolean
   def dependencies_ok? do
-    PythonWorker.has_module("pyexcel_ods3")
+    PythonPort.python_exists?() && PythonWorker.has_module("pyexcel_ods3")
   end
 
   @spec enabled? :: boolean
diff --git a/lib/service/export/participants/pdf.ex b/lib/service/export/participants/pdf.ex
index e1e8259dd..3d488e6c5 100644
--- a/lib/service/export/participants/pdf.ex
+++ b/lib/service/export/participants/pdf.ex
@@ -3,10 +3,8 @@ defmodule Mobilizon.Service.Export.Participants.PDF do
   Export a list of participants to PDF
   """
 
-  alias Mobilizon.Events
+  alias Mobilizon.{Events, Export, PythonPort, PythonWorker}
   alias Mobilizon.Events.Event
-  alias Mobilizon.Export
-  alias Mobilizon.PythonWorker
   alias Mobilizon.Storage.Repo
   alias Mobilizon.Web.ExportView
   alias Mobilizon.Web.Gettext, as: GettextBackend
@@ -105,7 +103,7 @@ defmodule Mobilizon.Service.Export.Participants.PDF do
 
   @spec dependencies_ok? :: boolean
   def dependencies_ok? do
-    PythonWorker.has_module("weasyprint")
+    PythonPort.python_exists?() && PythonWorker.has_module("weasyprint")
   end
 
   @spec enabled? :: boolean
diff --git a/lib/service/python_port.ex b/lib/service/python_port.ex
index 356c32c8a..af9aff69a 100644
--- a/lib/service/python_port.ex
+++ b/lib/service/python_port.ex
@@ -5,15 +5,23 @@ defmodule Mobilizon.PythonPort do
 
   use Export.Python
 
+  @python_path "/usr/bin/python3"
+
+  @doc """
+  Whether Python3 is installed
+  """
+  @spec python_exists? :: boolean
+  def python_exists? do
+    File.exists?(python_path())
+  end
+
   @doc """
   ## Parameters
     - path: directory to include in python path
   """
   @spec python_instance(String.t()) :: pid
   def python_instance(path) do
-    python = "/usr/bin/python3"
-
-    {:ok, pid} = Python.start(python: python, python_path: path)
+    {:ok, pid} = Python.start(python: python_path(), python_path: path)
 
     pid
   end
@@ -25,4 +33,12 @@ defmodule Mobilizon.PythonPort do
   def call_python(pid, module, function, arguments \\ []) do
     Python.call(pid, module, function, arguments)
   end
+
+  @spec python_path :: String.t()
+  defp python_path do
+    case get_in(Application.get_env(:mobilizon, __MODULE__), [:path]) do
+      path when is_binary(path) -> path
+      nil -> @python_path
+    end
+  end
 end