blog: 1.2 tasks

docs/blog/posts/devenv-v1.2-tasks.md

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+---
+draft: false
+date: 2024-09-24
+authors:
+  - domenkozar
+---
+
+# devenv 1.2: Tasks for convergent configuration with Nix
+
+It's often not possible to do configuration using Nix, which does [congruent configuration](https://constructolution.wordpress.com/2012/07/08/divergent-convergent-and-congruent-infrastructures/).
+<br>
+
+It's even more often practical to start with [convergent configuration](https://constructolution.wordpress.com/2012/07/08/divergent-convergent-and-congruent-infrastructures/)
+and translate it later into congruent if/when needed.
+<br>
+
+## enterShell
+
+For example, devenv provides [enterShell](/basics/) that corresponds to the shell code executed when you enter a developer environment.
+<br>
+
+In devenv itself, we have modules that set up things like pre-commit hooks or Python virtualenv as part of `enterShell`.
+<br>
+
+## Tasks
+
+We're introducing [tasks](/tasks/) to:
+<br>
+
+- Form dependencies between code, allowing us to parallelize setup as part of `enterShell` and execute tasks after something has been set up, like `python:virtualenv`.
+- Write automation in your favorite language, ditching shell code.
+- Gain visibility into what's happening inside your developer environment.
+
+
+## Usage
+
+For example if you'd like to execute python code after virtualenv has been created:
+
+```nix title="devenv.nix"
+{ pkgs, lib, config, ... }: {
+  languages.python.enable = true;
+  languages.python.venv.enable = true;
+
+  tasks = {
+    "python:setup" = {
+      exec = "python ${pkgs.writeText "setup.py" ''
+          print("hello world")
+      ''}";
+      after = [ "devenv:python:virtualenv" ];
+    };
+    "devenv:enterShell".after = [ "python:setup" ];
+  };
+}
+```
+
+`python:setup` task executes before `devenv:enterShell` but after `python:virtualenv` task:
+
+![Tasks interactive example](/assets/images/tasks.gif)
+
+
+For all supported use cases see [tasks documentation](/tasks/).
+
+
+## Task Server Protocol for SDKs
+
+We've talked to many teams that **dropped Nix** after a while and they usually fit into two categories:
+
+* 1) Maintaining **Nix was too complex** and the team didn't fully onboard, **creating friction inside the teams**.
+* 2) Went **all-in Nix** and it took **a big toll on the team productivity**.
+
+While devenv already addresses (1), bridging **the gap between Nix provided developer environments
+and existing devops tooling written in your favorite language is still an unsolved problem until now**.
+<br>
+
+We've designed [Task Server Protocol](https://github.com/cachix/devenv/issues/1457) so that you can write tasks
+using your existing automation by providing an executable that exposes the tasks to devenv:
+<br>
+
+```nix title="devenv.nix"
+{ pkgs, ... }:
+let
+  myexecutable = pkgs.rustPlatform.buildRustPackage rec {
+    pname = "foo-bar";
+    version = "0.1";
+    cargoLock.lockFile = ./myexecutable/Cargo.lock;
+    src = pkgs.lib.cleanSource ./myexecutable;
+  }
+in {
+  task.serverProtocol = [ "${myexecutable}/bin/myexecutable" ];
+}
+```
+
+In a few weeks we're planning to provide [Rust TSP SDK](https://github.com/cachix/devenv/issues/1457)
+with a full test suite so you can implement your own abstraction in your language of choice.
+<br>
+
+Tasks will enable you to use your favorite language to replace automation with
+`devenv tasks run <names>`.
+
+Tasks will enable us to use Rust instead of maintaining bash for glue code in devenv itself.
+
+## Upgrading
+
+If you run `devenv update` on your existing repository you should already be using tasks,
+without needing to upgrade to devenv 1.2.
+
+Domen