pqtools

Offline command-line and Python tooling for Power Query M source: parse, format, lint (check), safely rename a let binding, and run (eval) the transformation chain of a query against data you supply.

Unofficial. Not affiliated with or endorsed by Microsoft. Not a Power Query runtime - pq eval runs the transformation chain of a query locally; it never runs a connector (Web.Contents, Sql.Database, Csv.Document, ...). See Running M below.

Renamed. Published as mquery-toolkit 0.1.0 on 2026-09-03 and renamed the same day to pqtools to avoid a CLI name collision with the existing mquery package on PyPI (a Yara malware-query tool). mquery-toolkit 0.1.0 is yanked.

Install

pip install pqtools

Requires Node.js 22 or newer on PATH, or point MQUERY_NODE at a Node binary. The Microsoft parser and formatter packages are bundled inside the wheel (_bridge.cjs) - no npm install needed.

Quick start

# Parse to deterministic JSON (tokens, root kind, bindings/references)
pq parse query.pq

# Format - dry run prints a unified diff, nothing is written
pq format query.pq

# Format and write in place (atomic replace, preserves mode/newline/encoding)
pq format query.pq --write

# Lint, machine-readable output; exit code 2 if any diagnostic is severity=error
pq check query.pq --json

# Rename one top-level let binding - dry run first
pq rename query.pq --old OldName --new NewName

# Run a query's transformation chain locally, against your own data
pq eval report.pq --bind Source=data.csv

Python API

from pqtools import check, format_source, parse, rename, update_file

parsed = parse(source_text)  # dict: tokens, rootKind, analysis
formatted = format_source(source_text)  # formatted M source, same encoding
diagnostics = check(source_text, "query.pq")  # list[Diagnostic]
renamed = rename(source_text, "OldName", "NewName")

from pqtools.evaluate import evaluate

result = evaluate(source_text, bindings={"Source": [{"a": "1"}, {"a": "2"}]})

# File-level edit with the same dry-run/--write safety model as the CLI
diff = update_file(path, format_source)  # dry run: unified diff
diff = update_file(path, format_source, write=True)  # atomic write

Diagnostics

M002 and M003 are token-based checks over the parsed source, so they no longer fire inside comments or strings. Every matching occurrence is reported, one diagnostic per call site or literal.

check --json emits stable objects; check without --json prints file:line:column: severity code: message per diagnostic. The CLI exits 2 when any diagnostic has severity error, 0 otherwise.

Running M

pandas does not run Excel's formulas; it replaces Excel's data connections with your data, in Python. pq eval does the same for Power Query. A real M query is a Source = <connector>(...) step followed by a chain of Table.* transformations. pqtools cannot run the connector step - that is Microsoft's proprietary Mashup Engine, and this project does not reimplement it. But if you supply the source table, the rest of the transformation chain runs locally, offline, in Python:

pq eval report.pq --bind Source=data.csv

--bind NAME=PATH loads PATH (a .csv, read as a list of records with csv.DictReader - every value stays text, or a .json file, loaded as whatever it holds) and, wherever NAME is used as a let binding in the query, substitutes it directly - the binding's own right-hand-side expression (the connector call) is never evaluated, which is exactly what makes it irrelevant that pqtools cannot run it.

A table is simply list[dict[str, Any]] - a list of records. A record is dict[str, Any]. A list is list[Any]. That is the whole data model.

Worked example. Given report.pq:

let
  Source = Csv.Document(File.Contents("ignored.csv")),
  Kept = Table.SelectRows(Source, each [b] <> "y"),
  Renamed = Table.RenameColumns(Kept, {{"a", "id"}})
in
  Renamed

and data.csv:

a,b
1,x
2,y
3,z

$ pq eval report.pq --bind Source=data.csv
[{"b": "x", "id": "1"}, {"b": "z", "id": "3"}]

Csv.Document(File.Contents("ignored.csv")) is never called - ignored.csv is never opened. Source is the CSV you bound, Kept drops the b = "y" row, and Renamed renames a to id. Without --bind, the same query fails with a typed, exit-2 error naming the connector:

$ pq eval report.pq
error M_EVAL_UNSUPPORTED: Csv.Document is a connector - Power Query's Mashup
Engine runs it (Fabric or PQTest is the host that can); pqtools evaluates only
the transformation chain after you supply its result table with --bind

Supported: number/text/logical/null literals; + - * /; = <> < <= > >=; and or not; text &; if/then/else; let/in (lazy, memoised, correctly shadowed - a binding's expression is only ever evaluated once, and only if something actually references it); records ([a = 1]) and field access (r[a], r[a]?, and the each-scoped [a] shorthand for _[a]); lists ({1, 2}) and index access (l{0}, l{0}?); each and (x) => ... lambdas and calling them; try ... otherwise ...; and this builtin set (verbatim from pqtools.evaluate.BUILTINS, so it cannot drift out of sync with the code):

Text.From Text.Upper Text.Lower Text.Length Text.Combine Text.Contains
Text.Replace Text.Split Text.Start Text.End Text.Trim
Number.From Number.Round Number.Abs
List.Count List.Sum List.Max List.Min List.Average List.Transform List.Select
List.First List.Last List.Reverse List.Sort List.Contains List.Distinct
List.Range
Record.Field Record.FieldNames Record.HasFields Record.AddField
Record.RemoveFields
Table.FromRecords Table.ToRecords Table.RowCount Table.ColumnNames
Table.SelectRows Table.SelectColumns Table.RemoveColumns Table.RenameColumns
Table.AddColumn Table.TransformColumns Table.Sort Table.FirstN Table.LastN
Table.Distinct
Json.Document (text only - not the binary overload)
Logical.From

Everything else raises a typed UnsupportedError (M_EVAL_UNSUPPORTED) naming the exact construct - never approximated, never guessed at. That includes: any connector (Web.Contents, Sql.Database, File.Contents, Excel.Workbook, Csv.Document, Binary.* - the error names the construct and says it needs Fabric or PQTest, the two hosts that can actually run it); #shared; meta; type ascription (as, is, parameter/return types, type ...); ??; field projection (r[[a],[b]]); any identifier this evaluator does not know; and any builtin call with an argument shape not listed above. A wrong number would be worse than a refusal, so pqtools never approximates a connector's result or a builtin's documented behaviour - it either runs the real, documented semantics or it stops and tells you exactly where. max_steps (default 1,000,000, an evaluate() keyword argument) bounds the total number of AST nodes visited, so a runaway query cannot hang the caller either.

pq eval does not replace Power Query - it replaces the connector's data, the same trade pandas makes when it replaces a spreadsheet's data connections.

Safety model

• Dry-run by default. Every edit command (format, rename, replace-source) prints a unified diff and touches nothing unless --write is passed.
• --write is an atomic replace: the file is written to a sibling temp file, fsync'd, chmod'd to match the original, then moved into place with os.replace, after which the parent directory is fsync'd so the rename itself is durable.
• Layout is preserved: UTF-8 encoding, a leading BOM (present in every Power Query SDK connector file), newline convention (\n vs \r\n), final-newline state, and file mode all round-trip unchanged.
• Refuses symlinks and hardlinks - writes require a regular, single-link file.
• Detects concurrent change: the source is snapshotted before the transform and re-checked immediately before the atomic replace - this final snapshot check, not the lock, is the guarantee against lost updates; a change in that microsecond window raises SafeWriteError.
• Advisory lock while writing only - a --write call takes a cross-process advisory lock (fcntl/msvcrt) for the duration of the write and removes the lock file afterward, best-effort. It only serialises cooperating pq processes and is not a correctness guarantee: because the lock file is removed after use, a waiting process and a freshly started one can end up locking different inodes. Dry-run calls take no lock and create no lock file.
• This is not mandatory locking - no OS provides a portable mandatory lock, and the advisory lock is not itself the correctness guard. Use source control or external exclusive ownership for concurrent editors.

Limits

• Input and output are capped at 10 MiB.
• The Node subprocess is bounded to a 30 second timeout.
• Supported extensions: .pq, .m, .pqm, and any *.query.pq file.
• rename scope: exactly one unquoted top-level let binding. It refuses quoted identifiers (#"..."), record literals, lambda expressions, and non-ASCII source.
• Retry-After on the Fabric adapter must be whole seconds; HTTP-date values are rejected.
• Windows: two guarantees are weaker there and the code says so rather than pretending. A directory fsync after the atomic replace is impossible on Windows, so the rename is durable only as far as the filesystem makes it; and if the Node subprocess spawns a grandchild that inherits its stdout, a reader already blocked in ReadFile is not released by closing the pipe, so a timed-out call can run until that grandchild exits. Neither affects the bundled bridge, which spawns nothing.
• The parse response is roughly 40x the size of the source, and it is capped at 10 MiB, so parse, check, dependencies and rename fail with a typed NodeError on sources above roughly 240 KiB. format returns only text and is not affected.
• eval walks at most max_steps AST nodes (default 1,000,000, an evaluate() keyword argument, not yet exposed as a CLI flag) before raising a typed EvalError - a runaway or hostile query cannot hang the caller. A --bind file goes through the same --bind-only read path as everything else: 10 MiB cap, no symlinks, no non-regular files.

Working inside .xlsx and .pbix

pqtools can read the Power Query M source out of the real files it lives in - no need to open Excel or Power BI to see or lint a query.

Supported: pq check, pq parse, pq dependencies and pq eval accept an .xlsx, .pbix, .pbit, or a .pbip project (or its directory) directly. Each finds the Power Query section(s) inside the container and runs normally; check diagnostics and JSON output are labelled container!part (e.g. report.pbix!Formulas/Section1.m) so the output stays greppable across a batch of files. pq eval needs --member NAME to pick one shared query out of a container that holds more than one.

pq check report.pbix
pq check "Sales.pbip" --json
pq dependencies workbook.xlsx

Not supported (yet): writing back into a container. pq format, pq rename and pq replace-source refuse with a clear error on a container path. The underlying logic exists (pqtools.containers.write_sections) and is exercised in this repo's test suite against synthesized fixtures and a real Power BI Desktop sample - it rebuilds the container with only the M source changed, then re-reads its own output and verifies nothing else moved before ever touching disk - but it has not been validated against the wide range of real-world files this format can take, so it is deliberately kept out of the CLI.

pqtools is not a Power BI or Excel client: pq eval runs a query's own transformation chain against data you supply (see Running M) - it never opens a workbook, runs a connector, or writes anything back through the CLI.

Optional adapters

• fabric extra (pip install "pqtools[fabric]") - a Fabric Execute Query client that takes a caller-provided bearer token and an injected HTTP transport. It never manages credentials itself and is fully mocked in tests (no network access in the test suite).
• pqtest - a bounded wrapper around a user-installed Microsoft PQTest executable, Windows-only, pinned to version 2.155.2. It never downloads a binary; it only validates and runs one already on disk.

What it is not

• Not the Power Query Mashup Engine. pq eval runs a query's transformation chain against data you supply (see Running M); it never runs a connector, and anything it does not implement raises a typed error instead of approximating one.
• Not a Power BI or Fabric client, and it does not manage credentials.
• Not a general-purpose file editor - it only touches files with a supported extension and only through the safety model above.
• Not a replacement for Microsoft's own parser/formatter - it vendors and calls them directly rather than reimplementing M syntax.

Development

git clone https://github.com/GopalGB/pqtools
cd pqtools
python -m venv .venv && source .venv/bin/activate
pip install -e ".[dev,fabric]"
npm ci --ignore-scripts

pytest -q --cov=pqtools --cov-fail-under=80
mypy src
ruff check .
ruff format --check .
npm test
python -m build

License

MIT - see LICENSE. Bundled Microsoft packages (@microsoft/powerquery-parser, @microsoft/powerquery-formatter) and their dependencies are also MIT; see THIRD_PARTY_NOTICES.txt and NOTICE.