Conditional values

A YAML mapping where a value is expected means branches. Anything else is the literal value.

packages:
  - name: fd
    from:
      macos: brew
      default: [apt, zypper]   # a list is still just a value
    version: latest            # a scalar is still just a value

There is no when:, no select:, no matcher:. The shape carries the meaning, so the common case stays one line and the conditional case stays four.

Arm names come from a closed set

Arm keys are built-in names, or names you declare under targets:. Anything else is a parse error with a did-you-mean:

bedouin.yaml:6:7: packages[0].from: unknown arm `mcaos`
  did you mean: macos?

That is what the closed vocabulary buys: the vocabulary does not depend on the machine, so a config is valid or invalid identically everywhere. Only which arm wins varies. A typo cannot become a branch that silently never matches on a machine you are not sitting at.

Built-ins:

Kind	Names
os	macos, linux
distro	ubuntu, debian, fedora, opensuse, arch, other-distro
family	debian-like, rhel-like, suse-like, arch-like
arch	x86_64, arm64
combined	every name above, plus -x86_64 or -arm64

The more specific arm wins

Written order is irrelevant. Arms are compared by the facts they imply:

version:
  ubuntu: "1.80"      # implies os=linux, distro=ubuntu, distro_like=debian
  linux: stable       # implies os=linux
  default: latest

ubuntu contains everything linux contains and more, so it wins on Ubuntu — and the file can be sorted by a formatter without changing what it means.

Only genuinely incomparable arms are ambiguous, and those are a parse error:

version:
  macos: "1.80"       # os axis
  arm64: nightly      # arch axis -- neither contains the other

arms `macos` and `arm64` can both be true on one machine and neither is more
specific, so which one wins would be arbitrary.
  Write `macos-arm64:` for the machine where both hold

Declared targets

For axes no enum can know — a distro version, a hostname, an environment variable — name the condition once:

targets:
  - name: noble
    match: { distro: ubuntu, distro_version: ">=24.04" }
  - name: work
    match: { env: { BEDOUIN_PROFILE: work } }

packages:
  - name: neovim
    from: { noble: apt, default: cargo }   # apt's nvim is stale before 24.04

A declared target beats every built-in — you named it deliberately. Among several active targets, the one declared first wins.

match: accepts os, distro, distro_like, distro_version, arch, hostname and env. Version strings may lead with >=, >, <= or <.

only: — when an item should not exist at all

Arms choose between values. They cannot make an item not exist, and without that one config cannot cover Ubuntu and macOS:

packages:
  - name: xclip
    from: apt
    only: linux
  - name: mas
    from: brew
    only: [macos]

A pruned item’s other fields are never evaluated, so from: apt on a Linux-only package costs nothing on a Mac.

Two different things

A missing default: means you did not decide — that is a resolve-time error naming the arms available. only: means you decided the item does not exist here. They must not look alike, so they do not.

Saying it once

from: { macos: brew, debian-like: apt, suse-like: zypper } on twenty packages is twenty chances to get one wrong. Two ways out, both of which already work:

A variable holding the mapping. Variable values take arms like anything else, so this resolves per platform and reads well at the use site:

vars:
  pm: { macos: brew, debian-like: apt, suse-like: zypper }

packages:
  - name: jq
    from: "{{ vars.pm }}"
  - name: tree
    from: "{{ vars.pm }}"
  - name: zellij
    from: ["{{ vars.pm }}", cargo]      # still works in a fallback list

A YAML anchor, if you would rather not involve a variable. This is plain YAML and Bedouin never sees the difference:

packages:
  - name: jq
    from: &pm { macos: brew, debian-like: apt, suse-like: zypper }
  - name: tree
    from: *pm

The variable is usually the better one: it has a name, it shows up in plan -v, and an anchor has to be declared before its first use.

Templates

Values are minijinja templates, rendered after arm selection — so a losing arm is never evaluated, and a template only valid on one platform costs nothing on the others.

path: ["{{ home }}/.cargo/bin"]
version: "{{ env.ZELLIJ_VERSION | default('latest') }}"

Undefined names are an error, not an empty string: {{ hom }} would otherwise render /​.cargo/bin and ship a wrong PATH entry without a word.