This pull request has been mentioned on NixOS Discourse. There might be relevant details there:

https://discourse.nixos.org/t/running-evolution-without-gnome-is-it-sane-possible/8328/2

I tried running evolution-with-plugins but it does not seem to load the plugin at all. I don't see the option to add an EWS server.

@symphorien I was struggling to get evolution to "see" the evolution-ews plugin as well, unfortunately without much luck

To recapitulate, evolution-data-server looks for plug-ins in path that is hardcoded in its code so we either need to change the strings to a predefined value like /run/current-system/sw/lib/evolution-data-server or change it to a new store path where we install the plug-ins.

The former has an advantage that it can be done in advance during the initial build and there is no need to rebuild programs that depend on e-d-s (e.g. geary or gnome-shell) but it also requires a global location to install plug-ins.

The latter will allow us to have self-contained evolution-with-plugins but we will need to rebuild/replace all things that depend on evolution-data-server with a new derivation that combines e-d-s tree and plug-in trees and replaces all references to the original trees with the new $out. (We cannot just place it in different derivation since that would introduce a dependency cycle.)

And we cannot forget that evolution-ews installs to extension points for evolution in addition to e-d-s, so we would need to repeat these steps there too.

So I think the easiest way forward would be patching e-d-s and evolution to use /run/current-system/sw or some environment variable in addition to original paths as suggested in the ML but it will be tedious with so many supported extension points.

I can get the plugin to load this way:

diff --git a/pkgs/applications/networking/mailreaders/evolution/evolution-ews/default.nix b/pkgs/applications/networking/mailreaders/evolution/evolution-ews/default.nix
index ebad920d895..e4d5bbda2ef 100644
--- a/pkgs/applications/networking/mailreaders/evolution/evolution-ews/default.nix
+++ b/pkgs/applications/networking/mailreaders/evolution/evolution-ews/default.nix
@@ -3,11 +3,11 @@
 
 stdenv.mkDerivation rec {
   pname = "evolution-ews";
-  version = "3.36.5";
+  version = "3.36.4";
 
   src = fetchurl {
     url = "mirror://gnome/sources/${pname}/${stdenv.lib.versions.majorMinor version}/${pname}-${version}.tar.xz";
-    sha256 = "0h1wz4hxsasihdvvsaxnmzka4afjw7603gn0qcw8rxpw114ib1bl";
+    sha256 = "0zfq02h3r1qbxak04i49564q4s2ykvkgcyc3krjgndan9lq3kvvn";
   };
 
   nativeBuildInputs = [ cmake gettext intltool pkg-config ];
diff --git a/pkgs/applications/networking/mailreaders/evolution/evolution/default.nix b/pkgs/applications/networking/mailreaders/evolution/evolution/default.nix
index 819ab97ec34..d2d420fa78a 100644
--- a/pkgs/applications/networking/mailreaders/evolution/evolution/default.nix
+++ b/pkgs/applications/networking/mailreaders/evolution/evolution/default.nix
@@ -48,6 +48,10 @@ stdenv.mkDerivation rec {
     sha256 = "0vgd3i5zrs4r0i0700hhl89c66j41bgdzg9j8wdf0w8irlqj5xv2";
   };
 
+  patches = [
+    ./moduledir_from_env.patch
+  ];
+
   nativeBuildInputs = [
     cmake
     intltool
diff --git a/pkgs/applications/networking/mailreaders/evolution/evolution/moduledir_from_env.patch b/pkgs/applications/networking/mailreaders/evolution/evolution/moduledir_from_env.patch
new file mode 100644
index 00000000000..36b3bbacc1c
--- /dev/null
+++ b/pkgs/applications/networking/mailreaders/evolution/evolution/moduledir_from_env.patch
@@ -0,0 +1,21 @@
+diff --git a/src/shell/main.c b/src/shell/main.c
+index 5d089225ca..030908d684 100644
+--- a/src/shell/main.c
++++ b/src/shell/main.c
+@@ -407,7 +407,15 @@ create_default_shell (void)
+ 	}
+ 
+ 	/* Load all shared library modules. */
+-	module_types = e_module_load_all_in_directory (EVOLUTION_MODULEDIR);
++	const gchar *modules_directory = EVOLUTION_MODULEDIR;
++	const gchar *modules_directory_env;
++
++	modules_directory_env = g_getenv ("EVOLUTION_MODULEDIR");
++	if (modules_directory_env &&
++	    g_file_test (modules_directory_env, G_FILE_TEST_IS_DIR))
++		modules_directory = g_strdup (modules_directory_env);
++
++	module_types = e_module_load_all_in_directory (modules_directory);
+ 	g_list_free_full (module_types, (GDestroyNotify) g_type_module_unuse);
+ 
+ 	flags = G_APPLICATION_HANDLES_OPEN |
diff --git a/pkgs/applications/networking/mailreaders/evolution/evolution/wrapper.nix b/pkgs/applications/networking/mailreaders/evolution/evolution/wrapper.nix
index 1a0fdab7092..091f7b6ae2a 100644
--- a/pkgs/applications/networking/mailreaders/evolution/evolution/wrapper.nix
+++ b/pkgs/applications/networking/mailreaders/evolution/evolution/wrapper.nix
@@ -8,7 +8,12 @@ symlinkJoin {
 
   postBuild = ''
     wrapProgram $out/bin/evolution \
-      --set LD_LIBRARY_PATH "$out/lib"
+      --set LD_LIBRARY_PATH "$out/lib" \
+      --set EDS_ADDRESS_BOOK_MODULES "$out/lib/evolution-data-server/addressbook-backends/" \
+      --set EDS_CALENDAR_MODULES "$out/lib/evolution-data-server/calendar-backends/" \
+      --set EDS_CAMEL_PROVIDER_DIR "$out/lib/evolution-data-server/camel-providers/" \
+      --set EDS_REGISTRY_MODULES "$out/lib/evolution-data-server/registry-modules/" \
+      --set EVOLUTION_MODULEDIR "$out/lib/evolution/modules"
 
     LIBRARIES=$(ls -d ${lib.makeLibraryPath [evolution-ews]}/*)
     for library in $LIBRARIES; do

But I currently have no access to an ews account to test beyond "the option to add an ews account is offered to me"

@symphorien thanks, that is huge progress, I am building with your changes right now... and I have an exchange email address to test.
I'll be back after testing.

@symphorien I tested and I am unable to add an exchange account.
The "Exchange Webservices" option does appear in the "Receiving email" dialog, but when I finish adding all the required information and save nothing happens, after pressing the final "Done" button the app displays the same as before trying to add an exchange email. Namely no email account is added to the list of accounts.

The terminal does not reveal anything disturbing either...

maybe retry with G_MESSAGES_DEBUG=all ?

Thanks for the advice. I have applied that flag but I still can't see anything out of the ordinary. You can take a look here: https://pastebin.com/8DVFcK82

Looking at the environment of the various evolution-* processes it seems that they don't have the environment variable. Are they started by dbus ?

So I got it to work by also changing the module as well 92eda380bb3a61fe66ffd924ba84b708849c0fad . It's very hacky, I think the API of the module must be changed.

But you have to be very careful to not have anything depending on an old version of evolution-data-server in the system (I had installed gnome-calendar with home-manager) otherwise for a reason I cannot fathom, dbus starts the old (unwrapped) version of the evolution-data-server helpers.

So if it does not work for you, check with htop and lsof that the right helpers are launched.

Thanks a lot @symphorien ... I have tried with version 3.36.4 and 3.36.5 for evolution, evolution-data-server and evolution-ews and initially I could not get it working but apparently it needed a reboot.

So I pushed your changes in my branch and rebased to master. We finally have a working prototype for evolution-with-plugins.
We may be needing some more tests and code grooming.

I reworked the evolution data server module to install evolution plugins in 09f09facbd0

I reopened this properly as #103135