aivi.dbus

Types for D-Bus calls, signals, and values.

D-Bus is the message bus GNOME apps and system services use to talk to each other. This module gives you the data shapes for that conversation plus the DbusSource handle marker.

Current status: public D-Bus work goes through @source dbus; this module is the shared type vocabulary for that capability family.

Import

use aivi.dbus (
    DbusSource
    DbusValue
    DbusString
    DbusInt
    DbusBool
    DbusList
    DbusStruct
    DbusVariant
    DbusCall
    DbusSignal
    BusNameFlag
    AllowReplacement
    ReplaceExisting
    DoNotQueue
    BusNameState
    Owned
    Queued
    Lost
    DbusError
    NameNotOwned
    ServiceUnknown
    NoReply
    AccessDenied
    InvalidArgs
    DbusProtocolError
    DbusCallResult
    DbusTask
    DbusMatchRule
)

Overview

Type	Purpose
DbusValue	One value carried over the bus
DbusSource	Handle annotation for @source dbus
DbusCall	A method call request
DbusSignal	A broadcast message from a service
DbusMatchRule	Optional filters for selecting signals
BusNameFlag	How to request ownership of a bus name
BusNameState	Current ownership state of a bus name
DbusError	Structured D-Bus failures
DbusCallResult	Result of a call returning D-Bus values
DbusTask A	Background D-Bus work returning A

---

DbusValue

type DbusValue =
  | DbusString Text
  | DbusInt Int
  | DbusBool Bool
  | DbusList (List DbusValue)
  | DbusStruct (List DbusValue)
  | DbusVariant DbusValue

The current value model covers strings, integers, booleans, lists, structs, and variants.

• DbusList groups a list of bus values
• DbusStruct groups several fields into one ordered payload
• DbusVariant wraps a value when the protocol expects a runtime-typed value inside another value

use aivi.dbus (
    DbusValue
    DbusString
    DbusBool
    DbusStruct
)

value loginHint : DbusValue =
    DbusStruct [
        DbusString "ada@example.com",
        DbusBool True
    ]

---

DbusCall

type DbusCall = {
    destination: Text,
    path: Text,
    interface: Text,
    member: Text,
    body: List DbusValue
}

A method call sent to a D-Bus service.

• destination — the bus name to talk to
• path — the object path on that service
• interface — the interface name that owns the method
• member — the method name
• body — the ordered argument list

use aivi.dbus (DbusCall)

value pingCall : DbusCall = {
    destination: "org.freedesktop.DBus",
    path: "/org/freedesktop/DBus",
    interface: "org.freedesktop.DBus.Peer",
    member: "Ping",
    body: []
}

---

DbusSignal

type DbusSignal = {
    path: Text,
    interface: Text,
    member: Text,
    body: List DbusValue
}

A broadcast message emitted by a service. The shape is close to DbusCall, but there is no destination because signals are observed rather than directly addressed.

---

DbusMatchRule

type DbusMatchRule = {
    path: Option Text,
    interface: Option Text,
    member: Option Text
}

Optional filters for selecting only the signals you care about. Leave a field as None when you do not want to filter on it.

use aivi.dbus (DbusMatchRule)

value syncSignals : DbusMatchRule = {
    path: Some "/org/gnome/AiviMail/Daemon",
    interface: Some "org.gnome.AiviMail.IDaemon",
    member: Some "SyncStateChanged"
}

---

BusNameFlag

type BusNameFlag =
  | AllowReplacement
  | ReplaceExisting
  | DoNotQueue

Flags that control how a service asks for a bus name.

• AllowReplacement — let another process replace this name later
• ReplaceExisting — take over an existing name if the current owner allows it
• DoNotQueue — fail instead of waiting in a queue

---

BusNameState

type BusNameState =
  | Owned
  | Queued
  | Lost

Current state after requesting a bus name.

• Owned — this process owns the name now
• Queued — the request is waiting
• Lost — the name was lost or could not be kept

---

DbusError

type DbusError =
  | NameNotOwned Text
  | ServiceUnknown Text
  | NoReply
  | AccessDenied Text
  | InvalidArgs Text
  | DbusProtocolError Text

Structured failure reasons for D-Bus work.

• NameNotOwned Text — a required bus name is not owned
• ServiceUnknown Text — the destination service could not be found
• NoReply — the service did not answer in time
• AccessDenied Text — the bus rejected the request
• InvalidArgs Text — the call arguments were rejected
• DbusProtocolError Text — another protocol-level failure occurred

use aivi.dbus (
    DbusError
    NameNotOwned
    ServiceUnknown
    NoReply
    AccessDenied
    InvalidArgs
    DbusProtocolError
)

type DbusError -> Text
func describeBusError = error => error
 ||> NameNotOwned name     -> "name not owned: {name}"
 ||> ServiceUnknown name   -> "service not found: {name}"
 ||> NoReply               -> "service did not reply"
 ||> AccessDenied msg      -> "access denied: {msg}"
 ||> InvalidArgs msg       -> "invalid arguments: {msg}"
 ||> DbusProtocolError msg -> "D-Bus protocol error: {msg}"

---

DbusCallResult and DbusTask

type DbusCallResult = Result DbusError (List DbusValue)

type DbusTask A = Task DbusError A

Use DbusCallResult when you want the raw values returned by a method call. Use DbusTask A when a higher-level helper decodes those values into some application type A.