pyinc 2.0.1

A correctness-first incremental query engine for Python.

pyinc

pip install pyinc

pyinc is a pull-based incremental query kernel for Python. It memoizes the results of decorated functions, captures their dependencies as they execute, and on the next request re-runs only the work whose declared inputs actually changed. The design space is the one occupied by Salsa, Jane Street Incremental, and Bazel/Skyframe, adapted to the constraints of Python: mutable defaults, hidden ambient I/O, and pervasive object identity.

The library is pure-Python and stdlib-only, with zero runtime dependencies.

What pyinc is for

Programs in Python that cache derived results usually invalidate by hand: a watcher that clears a dict, a hash compared at the start of a function, a "stale?" boolean updated at known points. Every shortcut of that shape has a failure mode in which a real input changed but the cache did not notice, and the program silently uses a stale value.

pyinc exists so that class of problem can be solved without the caller having to reason about invalidation. The user declares base inputs, declares resources for external state (files, environment variables, directories), and writes queries as ordinary Python functions decorated with @query. The runtime captures the dependency graph as queries execute, stores frozen snapshots of every value crossing a cached boundary, and re-validates dependencies top-down on each request. Anything whose recorded dependencies are unchanged is reused. Anything whose recomputation produces a semantically equal result is backdated, so downstream consumers stay valid without re-running.

Quick example

from pyinc import Database, FileResource, query

_FILES = FileResource()

@query
def read_config(db, path):
    return _FILES.read(db, path)      # tracked file read

@query
def parse_names(db, path):
    text = read_config(db, path)
    return [line.strip() for line in text.splitlines() if line.strip()]

db = Database(mode="strict")
result = db.get(parse_names, "/tmp/names.txt")   # computes from scratch
result = db.get(parse_names, "/tmp/names.txt")   # reuses memo — file unchanged

# Edit the file: only affected queries re-execute.
# Comment-only edits can be backdated (early cutoff) with a cutoff= function.
# Raw open() inside a query raises UntrackedReadError.
# In strict mode, returned values are frozen — mutation raises TypeError.

See examples/correctness_demo.py for a walkthrough of backdating, mutation protection, untracked-read enforcement, and provenance inspection. The examples/ directory also contains focused scripts for the push-observer and artifact-store APIs, the mutable-graph boundary, the cross-run checkpoint API, the Jupyter notebook integration, and several shipped integrations.

What pyinc guarantees

pyinc guarantees from-scratch consistency: the result of incremental evaluation matches a fresh evaluation on the same declared inputs and resources. The guarantee holds when, and only when, three conditions hold:

1. Value boundary ownership — every value crossing a cached boundary is snapshot-safe: an immutable scalar, a tuple, a container that freeze can deep-convert (list → tuple, dict → FrozenDict, set → frozenset, dataclass → FrozenRecord), or a value handled by a registered ValueAdapter. Mutable graphs with shared identity or cycles are supported via FrozenGraph / FrozenRef and round-trip through the boundary without losing aliasing.
2. Tracked ambient reads — every read of external state inside a query goes through a Resource (or is explicitly declared via db.report_untracked_read(reason)). The runtime intercepts builtins.open, io.open, os.getenv, os.environ, os.listdir, os.scandir, and Path.iterdir while a query is executing, and raises UntrackedReadError on uses that escape this protocol.
3. Deterministic queries — given the same tracked dependencies, a query returns a semantically equal value. Mutable closure or global captures in a query definition are rejected at decoration time so memo reuse cannot silently depend on hidden Python object mutation.

The full contract — the soundness envelope, the three execution modes, the explicit out-of-scope cases, and the documented escape hatches — is in docs/kernel-contract.md.

Kernel surface

• @query for derived values, Input for explicit base leaves, optional eq= / cutoff= policies for custom equivalence and backdating, and ValueAdapter for custom snapshot-safe boundary types.
• FileResource, FileStatResource, EnvResource, and DirectoryResource for tracked external reads.
• Pull-based recomputation with revisions, dependency capture, red-green verification, and backdating (early cutoff) on semantic equality.
• strict, checked, and fast execution modes with explicit boundary semantics.
• Bounded query memoization via Database(max_query_nodes=...) (LRU at top-level request boundaries; inputs and resources stay resident).
• Atomic batch invalidation via Database.set_many(...) (single revision bump for any number of input updates).
• Database.dependency_graph() for a machine-readable export of all nodes and edges; Database.inspect(...) and Database.explain(...) for per-node provenance, observational and human-readable respectively; Database.statistics() and Database.query_profile() for aggregate counters and per-query timing.
• Database.observe(callback, query, *args, **kwargs) for push observers on query nodes. Events are delivered as QueryChangeEvent after the outermost request scope completes (so callbacks may safely re-enter the database) and fire only on executed decisions; reused and backdated decisions do not fire because the stored value did not move.
• Mutable object graphs across cached boundaries via FrozenGraph and FrozenRef snapshot variants. freeze memoizes mutable containers by id; thaw reconstructs identity faithfully via two-pass allocate-then-fill so a list-with-itself round-trips to an actual self-referential list. Pure trees pay no overhead and retain the flat snapshot shape.
• Content-addressed artifact storage via the ArtifactStore Protocol, with InMemoryArtifactStore and FileSystemArtifactStore implementations. Passing Database(store=...) writes the serialized snapshot bytes for every value crossing the membrane, keyed by its fingerprint_snapshot digest. serialize_snapshot and deserialize_snapshot expose the byte form to external callers and round-trip the full snapshot grammar.
• Database is thread-safe for concurrent use across instances and on a single shared instance. The ambient-read guard is installed once globally and dispatches per-context, so threads inside queries on different databases do not interfere with each other's enforcement.

Integrations

pyinc.integrations ships narrow, stdlib-only integrations that compose at the query layer. The kernel tracks cross-integration calls as ordinary dependency edges; no extra wiring is required.

• python_source — workspace-local module discovery, top-level imports and definitions, simple assignment tracking for export surfaces, and conservative import resolution with workspace / stdlib / installed / missing / ambiguous outcomes (stdlib and installed classification via composition with installed_packages; installed imports' resolved_path populated via deep_module_resolution).
• toml_config — single-file TOML inspection: section and key extraction, dependency and optional-dependency discovery, and tool-config discovery.
• requirements_txt — requirements parsing: normalized requirement specs, file references, index directives, editable installs, URL requirements, and deep_requirements_analysis for recursive -r / --requirement file following with cycle detection.
• installed_packages — installed package discovery via importlib.metadata-compatible .dist-info directories, stdlib module identification via sys.stdlib_module_names, and import-name resolution (stdlib / installed / unknown).
• deep_module_resolution — sys.path walking, .pth file processing with backdating on whitespace and comment-only edits, PEP 420 namespace package collection, and dotted-name → file resolution. Exposes resolve_module_path and deep_module_resolution_analysis.
• json_config — single-file JSON inspection: section and key extraction with type detection, nested-object traversal, and parse-error diagnostics.
• dependency_check — cross-integration dependency validation: composes installed_packages and python_source to detect undeclared imports and missing or version-mismatched packages.
• env_file — .env file parsing: key/value extraction with quoted and unquoted values, export prefix handling, and interpolation-reference detection.
• xml_config — XML inspection via xml.etree.ElementTree: element and attribute extraction, dot-path traversal, and namespace-aware tag normalization.
• csv_data — CSV/TSV structural analysis via stdlib csv: header detection, column discovery, delimiter sniffing, row counting, and inconsistent-column diagnostics.
• requirement_evaluation — PEP 440 version-specifier satisfaction and PEP 508 environment-marker evaluation; composes with requirements_txt and installed_packages to surface the effective applicable and satisfied requirement set for the current Python environment.
• symbol_resolution — workspace-wide symbol tables (module-level and class-level), cross-module re-export following with cycle detection, type-annotation text extraction via ast.unparse (no type evaluation), and a workspace-wide reverse-reference index for a given qualified name.
• notebook — Jupyter .ipynb analysis via stdlib json: per-cell type, source, and heading extraction; per-cell AST imports and definitions for code cells; and cutoff-based backdating that ignores outputs and execution_count, so re-running cells does not invalidate downstream consumers.

pyinc.integrations re-exports only the stable dataclass and result types and the high-level entrypoints. Low-level payload queries, decode helpers, and resource helpers remain experimental in their defining submodules.

Verification

• The kernel contract is summarized in docs/kernel-contract.md.
• The repository includes dedicated test modules for value semantics, runtime behavior, provenance and explanation formatting, property-based from-scratch consistency checks, and each shipped integration.
• The integration suites exercise strict, checked, and fast modes and compare incremental results against fresh recomputation over edit sequences.

The integration boundary is summarized in docs/integration-contract.md.

Diagnostics and escape hatches

• Database.inspect(...) is observational: it returns the last recorded provenance tree for a query key without forcing a fresh revalidation pass. Database.inspect_fresh(...) runs verification first and then returns the tree. See examples/inspect_fresh_demo.py.
• Query identity includes the function-definition payload. Captured ambient values contribute to the query fingerprint; mutable closure or global captures are rejected. Run pyinc.explain_query_captures(fn) before the first db.get(...) to see how each capture will be classified. See examples/capture_diagnostics.py.
• Database.report_untracked_read(reason) is an explicit impurity escape hatch. It marks the current query as always re-executing and disables backdating for that node, which is the right trade-off when a dependency is real but not resource-trackable. See examples/untracked_escape_hatch.py.
• The package ships inline typing metadata via py.typed.

Consumer tooling

LSP wiring and push-based filesystem watchers are deliberately out of scope for the kernel package. They live in a separate consumer layer, pyinc_tools, that builds only on the stable pyinc.integrations public surface:

• pyinc-tools analyze <root> runs one-shot or threaded --watch workspace analysis via a polling watcher.
• pyinc-tools lsp runs a stdio LSP server with document and workspace symbols, diagnostics, hover, goto-definition, and find-references, all backed by pyinc.integrations.symbol_resolution. The server starts a threaded filesystem watcher by default so external edits (e.g. git pull, formatter scripts) publish fresh diagnostics even when the editor does not emit workspace/didChangeWatchedFiles.

See docs/pyinc-tools-guide.md for install, editor wiring, the overlay model, and the supported-vs.-not-yet feature table.

Development

git clone https://github.com/Brumbelow/pyinc.git && cd pyinc
python3 -m venv .venv
. .venv/bin/activate
python3 -m pip install -e '.[dev]'
pytest -q
python3 -m mypy src tests
python3 -m ruff check src tests

The kernel contract is summarized in docs/kernel-contract.md. Integration API boundaries are summarized in docs/integration-contract.md. A guide to authoring new integrations is at docs/integration-authoring.md.