Chains & steps

A pipeline is a directed graph of steps. You build it by chaining method calls off a root and returning the leaf (or leaves). A step built off another runs after it and inherits its filesystem; steps returned together with no dependency between them run in parallel.

Starting a chain

hm.sh(...) starts a chain and sets its first command — shorthand for hm.scratch().sh(...).

sh(cmd, *, cwd=None, label=None, cache=None, env=None, timeout_seconds=None, image=None, key=None) -> Step

Parameter	Type	Default	Description
`cmd`	`str`	required	Shell command to run.
`cwd`	`str \| None`	`None`	Directory to run in, relative to the workspace root. Omit to run in the root.
`label`	`str \| None`	`None`	Human-facing label shown in the UI. Defaults to the command.
`cache`	`CachePolicy \| None`	`None`	Cache policy controlling result reuse across builds.
`env`	`dict[str, str] \| None`	`None`	Per-step environment variables merged on top of pipeline-level env.
`timeout_seconds`	`int \| None`	`None`	Hard wall-clock timeout in seconds.
`image`	`str \| None`	`None`	Local-mode Docker base image override for this step.
`key`	`str \| None`	`None`	Manual key override for this step in the v0 IR.

import harmont as hm

build = hm.sh("make build").sh("make test")

import { sh } from "@harmont/hm";

const build = sh("make build").sh("make test");

Forking and joining

Call .fork() to branch, and hm.wait() for a join barrier.

wait(*, continue_on_failure=False) -> Step

Parameter	Type	Default	Description
`continue_on_failure`	`bool`	`False`	When ``True``, the barrier passes even if upstream steps have failed, allowing cleanup or notification steps to run.

import harmont as hm

root = hm.sh("make deps")
lint = root.fork("lint").sh("make lint")
test = root.fork("test").sh("make test")

import { sh } from "@harmont/hm";

const root = sh("make deps");
const lint = root.fork({ label: "lint" }).sh("make lint");
const test = root.fork({ label: "test" }).sh("make test");

The full Step field and method list is in the chains reference.

Starting a chain

Forking and joining

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