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+---
+title: "Re-Inventing Task Runner That I Actually Used Daily"
+url: /re-inventing-task-runner-that-i-actually-used-daily.html
+date: 2023-05-31T12:21:10+02:00
+type: post
+draft: false
+---
+
+Couple of months ago I had this brilliant idea of re-inventing the wheel by
+making an alternative for make. And so I went. Boldly into the battle. And to my
+big surprise my attempt resulted in not a completely useless piece of software.
+
+My initial requirements were quite simple but soon grow into something more
+ambitious. And looking back I should have stuck to the simple version. My
+laziness was on my side this time though. Because I haven’t implemented some of
+the features I now realise I really didn’t need them and they would bog the
+whole program and make it be something it was never meant to be.
+
+My basic requirements were following:
+
+- Syntax should be a tiny bit inspired by Rake and Rakefiles.
+- Should borrow the overall feel of a unit test experience.
+- Using something like Python would be a bit of an overkill.
+- The program must be statically compiled, so it can run on same architecture
+  without libc, musl dependencies or things like that.
+- Install ruby for rake is a bit overkill and can not be done with certain
+  really lightweight distributions like Alpine Linux. This tool would be usable
+  on such lightweight systems for remote debugging.
+- I want to use it for more than just compiling things. I want to use it as an
+  entry-point into a project, and I want this to help me indirectly document the
+  project as well.
+- It should be an abstraction over bash shell or the default system shell.
+    - Each task essentially becomes its own shell instance.
+- Must work on Linux and macOS systems.
+- By default, running `erd` list all the available tasks (when I use make, I
+  usually put a disclaimer that you should check Makefile to see all available
+  target).
+- Should support passing arguments when you run it from a shell.
+- Normal variable as the same as environmental variables. There is no
+  distinction. Every variable is also essentially an environment variable and
+  can be used by other programs.
+- State between tasks is not shared, and this makes this “pure” shell instances.
+- Should be single-threaded for the start and later expanded with `@spawn`
+  command.
+- Variables behave like macros and are preprocessed before evaluation.
+- Should support something like `assure` that would check if programs like C
+  compiler or Python (whatever the project requires) are installed on a machine.
+
+Quite a reasonable list of requirements. I do this things already in my
+Makefiles or/and Bash scripts. But I would like to avoid repeating myself every
+time I start working on something new.
+
+So I started with the following syntax.
+
+```ruby
+@env on
+
+# Override the default shell.
+@shell /bin/bash
+
+# Assure that program is installed.
+@assure docker-compose pip python3
+
+# Load local dotenv files (these are then globally available).
+@dotenv .env
+@dotenv .env.sample
+@dotenv some_other_file
+
+# This are local variables but still accessible in tasks.
+@var HI = "hey"
+@var TOKEN = "sometoken"
+@var EMAIL = "m@m.com"
+@var PASSWORD = "pass"
+@var EDITOR = "vim"
+
+@task dev "Test chars .:'}{]!//" does
+  echo "..." $HI
+end
+
+@task clean "Cleans the obj files" does
+  rm .obj
+end
+
+@task greet "Greets the user" does
+  echo "Hi user $TOKEN or $WINDOWID $EMAIL"
+end
+
+@task stack "Starts Docker stack" does
+  docker-compose -f stack.yml up
+end
+
+@task todo "Shows all todos in source files and count them" does
+  grep -ir "TODO|FIXME" . | wc -l
+end
+
+@task test1 "For testing 1" does
+  unknown-command
+  echo "test1"
+  ls -lha
+end
+
+@task test2 "For testing 2" does
+  echo "test1"
+  ls -lha
+  docker-compose -f samples/stack.yml up
+end
+```
+
+One thing that I really like about Errand. Yes, this is what it is called. And
+it is available at https://git.mitjafelicijan.com/errand.git/about/. Moving
+on. One thing that I really like is that a task is a persistent shell. By that I
+mean, that the whole task, even if it contains multiple command in one shell.
+In make each line in a target is that and you need to combine lines or add `\`
+at the end of the line.
+
+```bash
+# How you do this things in make.
+target:
+        source .venv/bin/activate \
+        python script.py
+```
+
+This solves this problem. Consider each task and what is being executed in that
+task a shell that will only close when all the tasks are completed.
+
+By self-documenting I mean that if you are in a directory with `Errandfile` in,
+if you only type `erd` and press enter it should by default display all the
+possible targets. In make i was doing this by having a first target be something
+like `default` that echos the message “Check Makefile for all available target.”
+Because all of the tasks in Errand require a message I use that to display let’s
+call it table of contents.
+
+Because I don’t use any external dependencies this whole thing can be statically
+compiled. So that also checked one of the boxes.
+
+It works on Linux and on a Mac so that’s also a bonus. I don’t believe this
+would work on Windows machines because of the way that I use shell instances. By
+you could use something like Windows Subsystem for Linux and run it in
+there. That is a valid option.
+
+To finish this essay off, how was it to use it in “real life”. I have to be
+honest. Some of the missing features still bother me. `@dotenv` directive is
+still missing and I need to implement this ASAP.
+
+Another thing that needs to happen is support for streaming output. Currently
+commands like `docker-compose` that runs in foreground mode is not compatible
+with Errand. So commands that stream output are an issue.  I need to revisit how
+I initiate shell and how I read stdout and stderr.  But that shouldn’t be a
+problem.
+
+I have been very satisfied with this thing. I am pleasantly surprised by how
+useful it is. I really wanted to test this in the wild before I commit to it. I
+have more abandoned project than Google and it’s bringing a massive shame to my
+family at this point. So I wanted to be sure that this is even useful. And it
+actually is. Quite surprised at myself.
+
+I really need to package this now and write proper docs. And maybe rewrite
+tokeniser. Its atrocious right now. Site to behold! But that is an issue for
+another time.