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    podcomp

    A Compose Spec implementation that runs on Podman, written in MoonBit

    podman
    compose
    docker-compose
    containers
    cli
    moonbit
    Download zip
    Author
    Version
    0.1.2
    License
    Apache-2.0
    Repository
    Last updated
    16 hours ago
    Downloads
    3

    Dependencies

    #podcomp

    A Compose Spec implementation that runs on Podman, written in MoonBit. It reads the same compose.yaml / compose.yml / docker-compose.yml files Docker Compose reads, merges and interpolates them, and drives podman directly.

    One native binary. No daemon, no Python runtime, no background state.

    $ podcomp up -d
$ podcomp ps
$ podcomp logs -f web
$ podcomp down

    #Install

    # Installer script (Linux x86-64/arm64, macOS arm64)
curl -LsSf https://raw.githubusercontent.com/tomasky/podcomp/main/install.sh | bash

# npm
npm install -g @tomasko/podcomp

# From source
git clone https://github.com/tomasky/podcomp && cd podcomp
moon build --target native --release

    #What works

    podcomp is a port of the reference podman-compose behaviour, so the two can be used interchangeably for the common cases:

    • File discovery — compose.yaml, compose.yml, docker-compose.yml, or -f (repeatable, - reads standard input). Multiple files are merged with Compose's rules, and << merge keys are expanded.
    • Interpolation — .env files (via --env-file), the process environment, and the full ${VAR}, ${VAR:-default}, ${VAR-default}, ${VAR:?err}, ${VAR:+alt} and $$ operator set.
    • Profiles — services are selected with --profile and COMPOSE_PROFILES.
    • The service model — image, build, command, entrypoint, environment, env_file, ports, expose, volumes, tmpfs, networks, depends_on, healthcheck, labels, secrets, ulimits, deploy, resource limits, restart, user, workdir, hostname, dns, devices, sysctls, cap_add/cap_drop, and more.
    • Pods — the whole project runs in one pod (--infra=false), which is what makes service-name DNS work between containers. x-podman.in_pod and --in-pod control it.
    • Labels — the same io.podman.compose.* / com.docker.compose.* labels the reference writes, so an existing project is picked up unchanged.

    #Commands

    up        create and start the stack
down      stop and remove the stack
ps        list containers
logs      show container logs
start     start services
stop      stop services
restart   restart services
kill      kill services
rm        remove stopped containers
pull      pull service images
build     build service images
images    list service images
exec      run a command in a running container
run       run a one-off command in a new container
port      print the host port for a published port
pause     pause services
unpause   unpause services
config    print the merged compose file
version   show the version

    Global options include -f/--file, -p/--project-name, --profile, --env-file, --podman-path, --podman-args, --dry-run, --verbose and --in-pod. Run podcomp --help for the full list.

    --dry-run prints the podman invocations instead of running them, which is the quickest way to see what podcomp would do.

    #Example

    services:
  web:
    image: docker.io/library/nginx:alpine
    ports:
      - "8080:80"
    volumes:
      - ./html:/usr/share/nginx/html:ro
    depends_on:
      - db
  db:
    image: docker.io/library/postgres:16
    environment:
      POSTGRES_PASSWORD: secret
    volumes:
      - pgdata:/var/lib/postgresql/data
    healthcheck:
      test: ["CMD-SHELL", "pg_isready"]
      interval: 10s
      retries: 5

volumes:
  pgdata: {}

    $ podcomp --dry-run up
podman pod exists pod_demo
podman pod create --name=pod_demo --infra=false --share=
podman network exists demo_default
podman network create --label io.podman.compose.project=demo ... demo_default
podman create --name=demo_db_1 --pod=pod_demo ... docker.io/library/postgres:16
podman create --name=demo_web_1 --pod=pod_demo --requires=demo_db_1 ... nginx:alpine
podman start -a demo_db_1
podman start -a demo_web_1

    #Building

    Requires the MoonBit toolchain.

    moon check --target native --deny-warn
moon test --target native
moon build --target native --release
# _build/native/release/build/cmd/main/main.exe

    Releases are cut by pushing a v* tag; .github/workflows/release.yml builds static musl binaries for Linux and a native binary for macOS, attaches them to the GitHub Release, and publishes the npm launcher.

    #License

    Apache-2.0

    PodCompError

    source
    pub(all) suberror PodCompError {
      PodCompError(String)
    }

    The single error type the library raises. Every user-facing failure — a malformed compose file, a missing env var, a podman command that exits non-zero — arrives here as a message the CLI prints verbatim.

    CommandArgs

    source
    pub struct CommandArgs {
      services : Array[String]
      detach : Bool
      no_deps : Bool
      no_build : Bool
      build : Bool
      force_recreate : Bool
      no_recreate : Bool
      no_start : Bool
      volumes : Bool
      remove_orphans : Bool
      rmi : String?
      timeout : Int?
      follow : Bool
      tail : String?
      since : String?
      until : String?
      timestamps : Bool
      names : Bool
      no_color : Bool
      no_log_prefix : Bool
      quiet : Bool
      format : String?
      short : Bool
      signal : String?
      all : Bool
      index : Int
      protocol : String
      private_port : Int
      no_cache : Bool
      pull : String?
      build_arg : Array[String]
      quiet_pull : Bool
      wait : Bool
      wait_timeout : Int?
      name : String?
      entrypoint : String?
      env : Array[String]
      user : String?
      workdir : String?
      rm : Bool
      publish : Array[String]
      service_ports : Bool
      volume : Array[String]
      no_tty : Bool
      privileged : Bool
      force_local : Bool
      services_flag : Bool
      no_normalize : Bool
      pull_always : Bool
      abort_on_container_exit : Bool
      abort_on_container_failure : Bool
      exit_code_from : String?
      no_attach : Array[String]
      scale : String?
      renew_anon_volumes : Bool
      no_hosts : Bool
      cnt_command : Array[String]
    }

    Compose

    source
    pub struct Compose {
      project_name : String
      dirname : String
      files : Array[String]
      environ : Map[String, String]
      services : Map[String, 
    Yaml    ]
      deps : Map[String, Array[String]]
      container_names_by_service : Map[String, Array[String]]
      containers : Array[
    Yaml    ]
      container_by_name : Map[String, 
    Yaml    ]
      networks : Map[String, 
    Yaml    ]
      vols : Map[String, 
    Yaml    ]
      declared_secrets : Map[String, 
    Yaml    ]
      default_net : String?
      pods : Array[String]
      merged_yaml : 
    Yaml
      x_podman : Map[String, 
    Yaml    ]
      podman_version : String?
      pod_args : Array[String]
      env_file_cache : Map[String, Map[String, String]]
    }

    A loaded project, ready for a command to run against.

    GlobalOptions

    source
    pub struct GlobalOptions {
      files : Array[String]
      project_name : String?
      profiles : Array[String]
      env_files : Array[String]
      podman_path : String
      dry_run : Bool
      verbose : Bool
      no_ansi : Bool
      no_cleanup : Bool
      in_pod : String?
      pod_args : String?
      podman_args : Array[String]
      podman_cmd_args : Map[String, Array[String]]
    }

    Mount

    source
    type Mount

    A parsed volume/mount description.

    Podman

    source
    pub struct Podman {
      path : String
      dry_run : Bool
      verbose : Bool
      global_args : Array[String]
      cmd_args : Map[String, Array[String]]
    }

    A configured podman invocation.

    abspath

    source
    fn abspath(path : String) -> String

    An absolute version of path relative to the current directory.

    apply_merge_keys

    source

    Resolve YAML merge keys (<<: *anchor) in place, bottom-up.

    The parser keeps << as an ordinary key, so it is expanded here: a single mapping, or a sequence of mappings, contributes the keys the node does not already define. The << key is removed afterwards.

    ascii_lower

    source
    fn ascii_lower(s : String) -> String

    Lower-case ASCII only. MoonBit's core has no String::to_lowercase, and env-var names and boolean literals are ASCII anyway.

    assert_networks_and_volumes

    source
    async fn assert_networks_and_volumes(compose : Compose, podman : Podman, containers : Array[
    Yaml    ]) -> Unit

    Ensure every network and named volume the given containers need exists.

    The probes are deduplicated by name: a project with N containers on one network, or N services sharing one volume, pays one podman network exists / podman volume inspect instead of one per container.

    cmd_build

    source
    async fn cmd_build(compose : Compose, podman : Podman, args : CommandArgs) -> Int

    podcomp build

    cmd_config

    source
    fn cmd_config(compose : Compose, args : CommandArgs) -> Unit

    podcomp config

    cmd_down

    source
    async fn cmd_down(compose : Compose, podman : Podman, args : CommandArgs) -> Int

    podcomp down

    cmd_exec

    source
    async fn cmd_exec(compose : Compose, podman : Podman, args : CommandArgs) -> Int

    podcomp exec

    cmd_images

    source
    async fn cmd_images(compose : Compose, podman : Podman, args : CommandArgs) -> Int

    podcomp images

    cmd_kill

    source
    async fn cmd_kill(compose : Compose, podman : Podman, args : CommandArgs) -> Int

    podcomp kill

    cmd_logs

    source
    async fn cmd_logs(compose : Compose, podman : Podman, args : CommandArgs) -> Int

    podcomp logs

    cmd_pause_unpause

    source
    async fn cmd_pause_unpause(compose : Compose, podman : Podman, args : CommandArgs, action : String) -> Int

    podcomp pause / podcomp unpause

    cmd_port

    source
    async fn cmd_port(compose : Compose, podman : Podman, args : CommandArgs) -> Int

    podcomp port

    cmd_ps

    source
    async fn cmd_ps(compose : Compose, podman : Podman, args : CommandArgs) -> Int

    podcomp ps

    cmd_pull

    source
    async fn cmd_pull(compose : Compose, podman : Podman, args : CommandArgs) -> Int

    podcomp pull

    cmd_restart

    source
    async fn cmd_restart(compose : Compose, podman : Podman, args : CommandArgs) -> Int

    podcomp restart

    cmd_rm

    source
    async fn cmd_rm(compose : Compose, podman : Podman, args : CommandArgs) -> Int

    podcomp rm

    cmd_run

    source
    async fn cmd_run(compose : Compose, podman : Podman, args : CommandArgs) -> Int

    podcomp run

    cmd_start

    source
    async fn cmd_start(compose : Compose, podman : Podman, args : CommandArgs) -> Int

    podcomp start

    cmd_stop

    source
    async fn cmd_stop(compose : Compose, podman : Podman, args : CommandArgs) -> Int

    podcomp stop

    cmd_up

    source
    async fn cmd_up(compose : Compose, podman : Podman, args : CommandArgs) -> Int

    podcomp up

    cmd_version

    source
    async fn cmd_version(podman : Podman, args : CommandArgs) -> Unit

    podcomp version

    compose_env_file

    source
    fn compose_env_file(compose : Compose, path : String) -> Map[String, String]

    Read and parse an env_file, caching by path so a file shared by many services is read and parsed once.

    compose_labels

    source
    fn compose_labels(compose : Compose) -> Array[String]

    The project label prefix, matching what the reference implementation writes so podman ps --filter label=... finds containers either tool created.

    config_hash

    source
    fn config_hash(compose : Compose, service : 
    Yaml    ) -> String

    The config_hash of a service, used to decide whether a container is stale.

    container_mounts

    source
    fn container_mounts(compose : Compose, cnt : 
    Yaml    ) -> Array[Mount]

    Every mount of a container, parsed once so the args builder and the volume-creation pass share the same work.

    container_networks

    source
    fn container_networks(compose : Compose, cnt : 
    Yaml    ) -> Map[String, 
    Yaml    ]

    The networks a container joins: the service's networks, or the project's default network.

    container_to_args

    source
    fn container_to_args(compose : Compose, cnt : 
    Yaml    , detached : Bool, no_deps : Bool) -> Array[String] raise

    The argument list for podman create/run, following the reference implementation's ordering closely enough that the output is comparable.

    current_dir

    source
    fn current_dir() -> String

    The process working directory, or . when it cannot be read.

    default_compose_files

    source
    let default_compose_files : Array[String]

    The default compose file names, in the order Docker Compose probes them.

    dotenv_to_dict

    source
    fn dotenv_to_dict(path : String) -> Map[String, String]

    Read and parse a .env file, returning an empty map when it does not exist.

    error_text

    source
    fn error_text(error : Error) -> String

    Render any MoonBit error as a one-line message. A PodCompError already carries a human sentence, so it is unwrapped rather than printed with its constructor name attached.

    fail

    source
    fn fail(message : String) -> PodCompError

    Raise a PodCompError with a formatted message.

    format_name

    source
    fn format_name(compose : Compose, parts : Array[String]) -> String

    <project>_<parts...>.

    home_dir

    source
    fn home_dir() -> String

    The user's home directory, or an empty string.

    interp_str

    source
    fn interp_str(value : String, env : Map[String, String]) -> String raise

    Substitute every variable reference in one string.

    is_git_url

    source
    fn is_git_url(path : String) -> Bool

    Whether a build context is a remote git URL rather than a local directory.

    join_name_parts

    source
    fn join_name_parts(compose : Compose, parts : Array[String]) -> String

    Join name parts with the configured separator.

    load_compose

    source
    async fn load_compose(g : GlobalOptions) -> Compose

    Load a project. This reads files (and possibly standard input), so it is async; everything else about the model is synchronous.

    main_cli

    source
    async fn main_cli() -> Unit

    The entry point the executable calls.

    mount_arg

    source
    fn mount_arg(compose : Compose, cnt : 
    Yaml    , mount : Mount) -> Array[String]

    Translate one parsed mount into podman arguments.

    mount_target_of

    source
    fn mount_target_of(item : 
    Yaml    ) -> String?

    The container path of a short or long mount description.

    network_args

    source
    fn network_args(compose : Compose, cnt : 
    Yaml    ) -> Array[String]

    --network arguments for a container.

    network_name

    source
    fn network_name(compose : Compose, net : String) -> String

    The podman name of a top-level network, honouring name and external.

    new_command_args

    source
    fn new_command_args() -> CommandArgs

    new_compose

    source
    fn new_compose() -> Compose

    new_global_options

    source
    fn new_global_options() -> GlobalOptions

    new_podman

    source
    fn new_podman(g : GlobalOptions) -> Podman

    normalize_depends

    source

    Bring depends_on to its mapping form so two files can merge it.

    parse_dotenv

    source
    fn parse_dotenv(text : String) -> Map[String, String]

    Parse .env text. Later definitions override earlier ones; expansion sees the accumulated map.

    parse_short_mount

    source
    fn parse_short_mount(spec : String, basedir : String) -> Mount

    Parse the short mount form. A bare path is an anonymous volume; a path-like source is a bind mount; anything else is a named volume.

    path_abspath

    source
    fn path_abspath(base : String, path : String) -> String

    Resolve path against base when it is relative, then normalize.

    path_basename

    source
    fn path_basename(path : String) -> String

    The final component of a path.

    path_dirname

    source
    fn path_dirname(path : String) -> String

    The directory part of a path.

    path_expand_home

    source
    fn path_expand_home(path : String) -> String

    Expand a leading ~ into the user's home directory.

    path_join

    source
    fn path_join(a : String, b : String) -> String

    Join two path fragments with a single separator.

    path_normalize

    source
    fn path_normalize(path : String) -> String

    Collapse . and .. segments, preserving a leading /.

    podman_argv

    source
    fn podman_argv(podman : Podman, cmd : String, args : Array[String]) -> Array[String]

    The arguments after the podman binary: global options, the subcommand, then the command's configured options and the caller's own.

    podman_available

    source
    async fn podman_available(podman : Podman) -> Bool

    Whether podman is on the path and runnable.

    podman_output

    source
    async fn podman_output(podman : Podman, cmd : String, args : Array[String]) -> String

    Run podman and capture its standard output. Raises when the exit code is non-zero, with the captured standard error as the message.

    podman_run

    source
    async fn podman_run(podman : Podman, cmd : String, args : Array[String]) -> Int

    Run podman, inheriting the terminal. Returns the exit code.

    podman_try_output

    source
    async fn podman_try_output(podman : Podman, cmd : String, args : Array[String]) -> String?

    Run podman and capture its standard output, returning None when it fails. Used for existence probes (podman inspect, podman network exists).

    podman_version

    source
    async fn podman_version(podman : Podman) -> String?

    The podman version string, or None when podman is unavailable.
    fn print_help() -> Unit

    The podcomp --help text.

    rec_merge

    source
    fn rec_merge(target : Map[String, 
    Yaml    ], source : Map[String, 
    Yaml    ]) -> Unit raise

    Merge source into target in place.

    rec_subs

    source
    fn rec_subs(v : 
    Yaml    , env : Map[String, String]) -> 
    Yaml     raise

    Interpolate every string in a value tree.

    Within a service mapping, the service's own environment entries are added to the substitution scope first, so command: "$${PORT}" can see a PORT the service sets. Variables already in env win, matching the reference implementation.

    resolve_pod_args

    source
    fn resolve_pod_args(compose : Compose, cli_pod_args : String?) -> Array[String]

    Extra arguments passed to podman pod create.

    resolve_pod_name

    source
    fn resolve_pod_name(compose : Compose, cli_in_pod : String?) -> String?

    The pod name, honouring --in-pod, x-podman.in_pod, and the default of one pod per project.

    resolve_volume_name

    source
    fn resolve_volume_name(compose : Compose, cnt : 
    Yaml    , source : String, target : String) -> String

    The podman name of a named volume: name, the external name, or the project-prefixed default.

    shell_split

    source
    fn shell_split(command : String) -> Array[String]

    Split a string the way a shell would, honouring single and double quotes.

    short_mount_target

    source
    fn short_mount_target(spec : String) -> String?

    The container path in a SOURCE:TARGET[:OPTIONS] string.

    simple_hash

    source
    fn simple_hash(s : String) -> String

    A stable, short hash used for the config-hash label. Not cryptographic — it only has to change when the service configuration changes.

    str_to_seconds

    source
    fn str_to_seconds(text : String) -> Int?

    Convert "90s", "1m30s", "500ms" or a bare number to seconds.

    try_int_str

    source
    fn try_int_str(s : String) -> Int?

    Parse an integer, or None when the text is not one.

    version

    source
    let version : String

    Kept in sync with moon.mod, npmjs/package.json and the release tag. ci.yml fails when this drifts from moon.mod.

    version_at_least

    source
    fn version_at_least(have : String, want : String) -> Bool

    Whether a dotted version string is at least want ("5.6.0").

    y_arr

    source

    The array behind a Yaml::Array, if any.

    y_arr_v

    source

    y_bool

    source
    fn y_bool(v : 
    Yaml    ) -> Bool?

    A boolean, accepting the spellings Compose and podman accept.

    y_bool_v

    source
    fn y_bool_v(b : Bool) -> 
    Yaml

    y_clone

    source

    Deep copy. Merge mutates its target, so every value copied in must be owned.

    y_dict

    source

    The norm_as_dict of the reference implementation: ["k=v", "k2"] becomes {k: v, k2: null}. Bare keys keep a Yaml::Null value so the original spelling survives a round-trip.

    y_dump

    source
    fn y_dump(v : 
    Yaml    ) -> String

    Render a value as YAML text, without the leading --- document marker.

    y_env_list

    source
    fn y_env_list(v : 
    Yaml    ) -> Array[String]

    Turn a mapping into a list of k=v (or bare k) strings. This is the norm_as_list(norm_as_dict(x)) shape container_to_args wants.

    y_get

    source

    Look a key up in a mapping value. None for a non-mapping or a missing key.

    y_int

    source
    fn y_int(v : 
    Yaml    ) -> Int?

    An integer, accepting ints, floats and numeric strings.

    y_int_v

    source
    fn y_int_v(i : Int) -> 
    Yaml

    y_list

    source

    The norm_as_list of the reference implementation: a scalar becomes a one-element list, a map becomes ["k=v", "k2"], null becomes empty.

    y_list_str

    source
    fn y_list_str(v : 
    Yaml    ) -> Array[String]

    y_list, keeping only the scalars.

    y_map

    source

    The map behind a Yaml::Map, if any.

    y_map_v

    source

    y_null

    source

    y_obj

    source

    Build a mapping value from key/value pairs.

    y_str

    source
    fn y_str(v : 
    Yaml    ) -> String?

    A scalar rendered as text. None for collections and nulls.

    y_str_or

    source
    fn y_str_or(v : 
    Yaml    , fallback : String) -> String

    A scalar rendered as text, or fallback.

    y_str_v

    source
    fn y_str_v(s : String) -> 
    Yaml

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