tasks: pickup outgoing task dependencies

[sandydoo]

I think we're running the tasks in reverse order after the toposort. The following tasks are speced to run after enterShell, but they instead run before.

This PR lets the graph traversal visit both incoming and outgoing edges.
Traversing all the edges of a node allows picking up tasks that are only specified to run after the current node. For example:

tasks."my-app:after-venv" = {
  exec = "echo hello";
  after = [ "devenv:python:virtualenv" ];
};

Previously, the only way to do this was to also use before to add this dependency to the graph, usually via devenv:enterShell. This change also allows running tasks after devenv:enterShell.

Fixes #1557.

TODO

While this change makes setting up tasks more predictable, we'll need to make this behavior configurable to support one-off tasks. You might want to run just the specified task, or all the tasks up to the specified task.

This also opens up the question of different types of constraints, e.g. ordering vs dependency. systemd has After and Requires.

• Update existing tests

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[sandydoo]

While this change makes setting up tasks more predictable, we'll need to make this behavior configurable to support one-off tasks. You might want to run just the specified task, or all the tasks up to the specified task.

This also opens up the question of different types of constraints, e.g. ordering vs dependency. systemd has After and Requires.

We need to brainstorm on this one.

Only doing incoming (outgoing) edges means that only before (after) works for adding a task to the graph.

Using undirected lets us traverse the entire graph, at the cost of not letting us run subgraphs of tasks. We can't tell the difference between ordering hints and requirements.

In this example, if we run devenv:enterShell in the context of launching a shell, we want to run every task reachable from it. This includes the tasks specified using after: app:afterVenv and app:afterShell.

graph TD;
    devenv:python:virtualenv-->app:afterVenv;
    devenv:python:virtualenv-->devenv:enterShell;
    devenv:enterShell-->app:afterShell;
    devenv:git-hooks:install-->devenv:enterShell;

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But if we run just app:afterVenv, we may reasonable expect to only run that and devenv:python:virtualenv. Now devenv:python:virtualenv might not make sense without devenv:enterShell, but that's a spec issue.

graph TD;
    devenv:python:virtualenv-->app:afterVenv;
    devenv:python:virtualenv-->devenv:enterShell;
    devenv:enterShell-->app:afterShell;
    devenv:git-hooks:install-->devenv:enterShell;
    style app:afterVenv fill:#0095b6,stroke-width:0,color:white
    style devenv:python:virtualenv fill:#0095b6,stroke-width:0,color:white

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[domenkozar]

@sandydoo maybe hooks should do the former while devenv tasks run do the latter?

[domenkozar]

@sandydoo shall we open an issue and merge this?

[sandydoo]

@sandydoo maybe hooks should do the former while devenv tasks run do the latter?

Yeah, we need a CLI flag to modify the "traversal strategy"