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-rw-r--r--nixos/modules/programs/less.nix134
1 files changed, 134 insertions, 0 deletions
diff --git a/nixos/modules/programs/less.nix b/nixos/modules/programs/less.nix
new file mode 100644
index 00000000000..794146b19fa
--- /dev/null
+++ b/nixos/modules/programs/less.nix
@@ -0,0 +1,134 @@
+{ config, lib, pkgs, ... }:
+
+with lib;
+
+let
+
+  cfg = config.programs.less;
+
+  configText = if (cfg.configFile != null) then (builtins.readFile cfg.configFile) else ''
+    #command
+    ${concatStringsSep "\n"
+      (mapAttrsToList (command: action: "${command} ${action}") cfg.commands)
+    }
+    ${if cfg.clearDefaultCommands then "#stop" else ""}
+
+    #line-edit
+    ${concatStringsSep "\n"
+      (mapAttrsToList (command: action: "${command} ${action}") cfg.lineEditingKeys)
+    }
+
+    #env
+    ${concatStringsSep "\n"
+      (mapAttrsToList (variable: values: "${variable}=${values}") cfg.envVariables)
+    }
+  '';
+
+  lessKey = pkgs.writeText "lessconfig" configText;
+
+in
+
+{
+  options = {
+
+    programs.less = {
+
+      # note that environment.nix sets PAGER=less, and
+      # therefore also enables this module
+      enable = mkEnableOption "less";
+
+      configFile = mkOption {
+        type = types.nullOr types.path;
+        default = null;
+        example = literalExpression ''"''${pkgs.my-configs}/lesskey"'';
+        description = ''
+          Path to lesskey configuration file.
+
+          <option>configFile</option> takes precedence over <option>commands</option>,
+          <option>clearDefaultCommands</option>, <option>lineEditingKeys</option>, and
+          <option>envVariables</option>.
+        '';
+      };
+
+      commands = mkOption {
+        type = types.attrsOf types.str;
+        default = {};
+        example = {
+          h = "noaction 5\\e(";
+          l = "noaction 5\\e)";
+        };
+        description = "Defines new command keys.";
+      };
+
+      clearDefaultCommands = mkOption {
+        type = types.bool;
+        default = false;
+        description = ''
+          Clear all default commands.
+          You should remember to set the quit key.
+          Otherwise you will not be able to leave less without killing it.
+        '';
+      };
+
+      lineEditingKeys = mkOption {
+        type = types.attrsOf types.str;
+        default = {};
+        example = {
+          e = "abort";
+        };
+        description = "Defines new line-editing keys.";
+      };
+
+      envVariables = mkOption {
+        type = types.attrsOf types.str;
+        default = {
+          LESS = "-R";
+        };
+        example = {
+          LESS = "--quit-if-one-screen";
+        };
+        description = "Defines environment variables.";
+      };
+
+      lessopen = mkOption {
+        type = types.nullOr types.str;
+        default = "|${pkgs.lesspipe}/bin/lesspipe.sh %s";
+        defaultText = literalExpression ''"|''${pkgs.lesspipe}/bin/lesspipe.sh %s"'';
+        description = ''
+          Before less opens a file, it first gives your input preprocessor a chance to modify the way the contents of the file are displayed.
+        '';
+      };
+
+      lessclose = mkOption {
+        type = types.nullOr types.str;
+        default = null;
+        description = ''
+          When less closes a file opened in such a way, it will call another program, called the input postprocessor, which may  perform  any  desired  clean-up  action (such  as deleting the replacement file created by LESSOPEN).
+        '';
+      };
+    };
+  };
+
+  config = mkIf cfg.enable {
+
+    environment.systemPackages = [ pkgs.less ];
+
+    environment.variables = {
+      LESSKEYIN_SYSTEM = toString lessKey;
+    } // optionalAttrs (cfg.lessopen != null) {
+      LESSOPEN = cfg.lessopen;
+    } // optionalAttrs (cfg.lessclose != null) {
+      LESSCLOSE = cfg.lessclose;
+    };
+
+    warnings = optional (
+      cfg.clearDefaultCommands && (all (x: x != "quit") (attrValues cfg.commands))
+    ) ''
+      config.programs.less.clearDefaultCommands clears all default commands of less but there is no alternative binding for exiting.
+      Consider adding a binding for 'quit'.
+    '';
+  };
+
+  meta.maintainers = with maintainers; [ johnazoidberg ];
+
+}