chromium: add support for external extensions

This allows the installation of external (outside of the Chrome Web
Store) extensions, both local and remote.

PR #1648

modules/programs/chromium.nix

@@ -25,20 +25,73 @@ let
 
       extensions = mkOption {
         inherit visible;
-        type = types.listOf types.str;
+        type = with types;
+          let
+            extensionType = submodule {
+              options = {
+                id = mkOption {
+                  type = strMatching "[a-zA-Z]{32}";
+                  description = ''
+                    The extension's ID from the Chome Web Store url or the unpacked crx.
+                  '';
+                  default = "";
+                };
+
+                updateUrl = mkOption {
+                  type = str;
+                  description = ''
+                    URL of the extension's update manifest XML file. Linux only.
+                  '';
+                  default = "https://clients2.google.com/service/update2/crx";
+                  visible = pkgs.stdenv.isLinux;
+                  readOnly = pkgs.stdenv.isDarwin;
+                };
+
+                crxPath = mkOption {
+                  type = nullOr path;
+                  description = ''
+                    Path to the extension's crx file. Linux only.
+                  '';
+                  default = null;
+                  visible = pkgs.stdenv.isLinux;
+                };
+
+                version = mkOption {
+                  type = nullOr str;
+                  description = ''
+                    The extension's version, required for local installation. Linux only.
+                  '';
+                  default = null;
+                  visible = pkgs.stdenv.isLinux;
+                };
+              };
+            };
+          in listOf (coercedTo str (v: { id = v; }) extensionType);
         default = [ ];
         example = literalExample ''
           [
-            "chlffgpmiacpedhhbkiomidkjlcfhogd" # pushbullet
-            "mbniclmhobmnbdlbpiphghaielnnpgdp" # lightshot
-            "gcbommkclmclpchllfjekcdonpmejbdp" # https everywhere
-            "cjpalhdlnbpafiamejdnhcphjbkeiagm" # ublock origin
+            { id = "cjpalhdlnbpafiamejdnhcphjbkeiagm"; } # ublock origin
+            {
+              id = "dcpihecpambacapedldabdbpakmachpb";
+              updateUrl = "https://raw.githubusercontent.com/iamadamdev/bypass-paywalls-chrome/master/updates.xml";
+            }
+            {
+              id = "aaaaaaaaaabbbbbbbbbbcccccccccc";
+              crxPath = "/home/share/extension.crx";
+              version = "1.0";
+            }
           ]
         '';
         description = ''
           List of ${name} extensions to install.
           To find the extension ID, check its URL on the
           <link xlink:href="https://chrome.google.com/webstore/category/extensions">Chrome Web Store</link>.
+          </para><para>
+          To install extensions outside of the Chrome Web Store set
+          <literal>updateUrl</literal> or <literal>crxPath</literal> and
+          <literal>version</literal> as explained in the
+          <link xlink:href="https://developer.chrome.com/docs/extensions/mv2/external_extensions">Chrome
+          documentation</link>.
         '';
       };
     };
@@ -61,12 +114,16 @@ let
       else
         "${config.xdg.configHome}/${browser}";
 
-      extensionJson = ext: {
-        name = "${configDir}/External Extensions/${ext}.json";
-        value.text = builtins.toJSON {
-          external_update_url =
-            "https://clients2.google.com/service/update2/crx";
-        };
+      extensionJson = ext:
+        with builtins; {
+          name = "${configDir}/External Extensions/${ext.id}.json";
+          value.text = toJSON
+            (if (isPath ext.crxPath && isString ext.version) then {
+              external_crx = ext.crxPath;
+              external_version = ext.version;
+            } else {
+              external_update_url = ext.updateUrl;
+            });
         };
 
     in mkIf cfg.enable {