acmt001-lsp 0.0.1

Language Server Protocol (LSP) server for authoring acmt001 ISO 20022 Account Management data files.

Acmt001-lsp: A Language Server for Authoring ISO 20022 Account-Data Files

Real-time editor help for ISO 20022 account-data files — diagnostics, completion, and hover as you author the JSON records that drive acmt message generation.

Latest release: v0.0.1 — a pygls-based Language Server with schema + IBAN/BIC/LEI diagnostics, field and message-type completion, and schema-description hover, all backed by acmt001.services. See what's new →

Contents

• Overview
• Install
• Quick Start
  • Editor wiring
• Features
• Using the helpers
• Examples
• Development
• Licence
• Contribution
• Acknowledgements

Overview

A Language Server speaks the Language Server Protocol (LSP) — the editor-agnostic protocol that lets a single backend deliver diagnostics, completion, hover, and more to any LSP client (VS Code, Neovim, Helix, Emacs, …). Acmt001-lsp is that backend for account-data JSON files: the JSON arrays of flat account records that drive ISO 20022 acmt message generation in the acmt001 suite.

• Website: https://acmt001.com
• Source code: https://github.com/sebastienrousseau/acmt001-lsp
• Bug reports: https://github.com/sebastienrousseau/acmt001-lsp/issues

It gives editors three features as you type, all backed by acmt001.services so they behave identically to the CLI, REST API, and MCP server:

• Diagnostics — each record is validated against a message type's input JSON Schema, and any IBAN / BIC / LEI identifier values are additionally checked with the dedicated validators.
• Completion — every input field (with its description) plus the list of supported acmt message types.
• Hover — the schema description for the field under the cursor.

The intended message type defaults to acmt.007.001.05 (Account Opening Request); the pure helpers accept a message_type argument so a different type can be configured.

Acmt001-lsp is part of the acmt001 suite — a set of independently installable packages (all Python 3.10+) sharing the acmt001.services layer:

Package	Role
acmt001	Core library + Click CLI + FastAPI REST API
acmt001-mcp	Model Context Protocol server (for AI agents)
acmt001-lsp	Language Server Protocol server (this package)

flowchart LR
    A["Editor (VS Code / Neovim / …)"] -->|LSP over stdio| B["acmt001-lsp"]
    B -->|compute_diagnostics / completion_items / hover_text| C["acmt001.services"]
    C -->|schema + IBAN/BIC/LEI validation| B
    B -->|diagnostics · completion · hover| A

Install

Acmt001-lsp runs on macOS, Linux, and Windows and requires Python 3.10+ and pip. It pulls in the core acmt001 library and pygls automatically.

python -m pip install acmt001-lsp

Verify the installation:

python -c "import acmt001_lsp; print('acmt001-lsp', acmt001_lsp.__version__)"

Using an isolated virtual environment (recommended)

python -m venv venv
source venv/bin/activate        # macOS/Linux
venv\Scripts\activate           # Windows
python -m pip install -U acmt001-lsp

Quick Start

The package installs an acmt001-lsp console entry point that starts the language server over stdio:

acmt001-lsp

The command speaks LSP on stdin/stdout — it is meant to be launched by your editor's LSP client, not used interactively. Point your editor at it for JSON account-data files and you get diagnostics, completion, and hover as you type.

Editor wiring

Register acmt001-lsp as the server cmd for JSON files in your editor's LSP client.

Neovim (built-in vim.lsp.config)

vim.lsp.config["acmt001"] = {
  cmd = { "acmt001-lsp" },
  filetypes = { "json" },
  root_markers = { ".git" },
}
vim.lsp.enable("acmt001")

VS Code (generic LSP client)

Configure a generic LSP client extension to spawn the acmt001-lsp command over stdio for the json language, or wrap it in a small extension whose serverOptions is { command: "acmt001-lsp", transport: TransportKind.stdio }.

Open a JSON array of account records and the server validates each record on open and on every change, surfaces completion for field names and message types, and shows schema descriptions on hover.

Features

For account-data JSON files (a JSON array of flat account records, or a single record object treated as one record):

• Diagnostics — schema validation reports missing required fields, wrong types, and pattern/length violations; identifier fields (account_id, account_servicer_bic, org_id_lei, account_owner_lei) are additionally checked as IBAN / BIC / LEI. Malformed JSON yields a single syntax diagnostic at the offending position.
• Completion — every input field for the message type (with its schema description as the detail) plus every supported acmt message type.
• Hover — the schema description for the field name under the cursor.

The feature logic lives in pure, importable helpers (compute_diagnostics, completion_items, hover_text) backed by the shared acmt001.services layer, so editor behaviour stays in lockstep with the CLI, REST API, and MCP server. The LSP handlers are thin glue that map those plain dicts to lsprotocol types.

Using the helpers

Because the feature logic is pure, you can call it directly — no editor or server process required. This is exactly what the server runs on each edit:

import json

from acmt001_lsp.server import (
    completion_items,
    compute_diagnostics,
    hover_text,
)

# A complete, valid account record produces no diagnostics.
valid_doc = json.dumps(
    [
        {
            "msg_id": "ACMT-MSG-0001",
            "creation_date_time": "2026-01-15T10:30:00",
            "process_id": "ACMT-PRC-0001",
            "account_id": "GB29NWBK60161331926819",
            "account_currency": "EUR",
            "account_name": "Treasury Operating Account",
            "account_type_cd": "CACC",
            "account_servicer_bic": "NWBKGB2LXXX",
            "account_owner_name": "Acme Embedded Finance Ltd",
            "account_owner_country": "GB",
            "org_full_legal_name": "Acme Embedded Finance Limited",
            "org_id_lei": "5493001KJTIIGC8Y1R12",
        }
    ]
)
assert compute_diagnostics(valid_doc) == []

# Missing required fields are reported as errors.
missing = json.dumps([{"msg_id": "ONLY-ID"}])
print(len(compute_diagnostics(missing)), "issue(s)")

# An invalid BIC is flagged as a warning.
bad_bic = json.dumps([{"account_servicer_bic": "INVALID"}])
print(compute_diagnostics(bad_bic)[:1])

# Completion offers field names and message types; hover shows descriptions.
items = completion_items()
print(len(items), "completion items, e.g.", items[0]["label"])
print(hover_text("account_servicer_bic"))   # -> the field's schema description
print(hover_text("nope"))                    # -> None

Each diagnostic is a plain dict — {"line": int, "character": int, "severity": "error" | "warning", "message": str} — which the server maps to lsprotocol Diagnostic objects before publishing.

See examples/lsp_helpers.py for the full runnable script.

Examples

The examples/ directory contains a self-contained, runnable script for the helper API:

Example	Demonstrates
lsp_helpers.py	The LSP diagnostics / completion / hover helpers

git clone https://github.com/sebastienrousseau/acmt001-lsp.git && cd acmt001-lsp
python examples/lsp_helpers.py

Development

Acmt001-lsp uses Poetry and mise.

git clone https://github.com/sebastienrousseau/acmt001-lsp.git && cd acmt001-lsp
mise install
poetry install
poetry shell

A Makefile orchestrates the quality gates (kept in lockstep with CI):

make check        # all gates (REQUIRED before commit)
make test         # pytest
make lint         # ruff + black
make type-check   # mypy --strict
make examples     # run the example script

Licence

Licensed under the Apache Licence, Version 2.0. Any contribution submitted for inclusion shall be licensed as above, without additional terms.

Contribution

Contributions are welcome — see the contributing instructions. Thanks to all contributors.

Acknowledgements

Built on pygls and lsprotocol by the Open Law Library, and on the core acmt001 library that powers the shared service layer.