web-fetcher/SCOPE.md
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WEBFETCH-WP-0003: Forgejo CI, org licence, inbox acks, progress
- .forgejo/workflows/test.yaml: offline tests on Python 3.10 and 3.13
- LICENSE: Target Revenue Source License V1C1 (org-wide preliminary licence)
- pyproject: license field; AGENTS/SCOPE: CI and licence facts

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Assistant: claude-code
Assistant-Model: opus
Assistant-Process: 153021@bnt-lap001
Assistant-Session: 46917be4-6400-4106-b8b7-61953a0caf24
2026-10-19 14:27:11 +02:00

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# SCOPE
> What the repository **is** today. What it aspires to be is in `INTENT.md`;
> the gap between the two is tracked in `workplans/`.
## One-liner
Standard-library fetching of data from public APIs and web data files into
provenance-carrying `Observation` records, for research repositories.
## Core Idea
Research repos declare *what* they need as JSON fetch specs; web-fetcher fetches
each URL and returns `Observation` records with the value plus URL, retrieval
time and the SHA-256 of the raw payload. Missing data becomes `not_found`,
failures become `error`; a failing spec never aborts the run.
## What Exists
- `Observation` record and `fetch_bytes` HTTP GET (`web_fetcher/core.py`):
sets `retrieved_at`, `payload_sha256` and — when the server sends
`Last-Modified` — `published`. Retries only connection errors, timeouts and
HTTP 429/5xx (exponential 1.5 s, 3 s, or `Retry-After` capped at 120 s);
other HTTP errors fail immediately.
- Cache and replay: `--cache DIR` stores `<sha256>.bin` and an `index.jsonl`
entry per fetch; `--replay DIR` serves URLs from it without network,
verifying hashes and keeping the original retrieval time. The most recent
entry per URL wins, so exact reproduction needs one cache directory per run.
- Spec dispatch (`web_fetcher/registry.py`): unknown adapters, fetch failures
and parse errors become `error` observations; an `ok` value without
`source` becomes `error`.
- Adapters:
- `eurostat` (JSON-stat 2.0) — names its own source; `published` from the
dataset's `updated`.
- `http_json` — dotted path lookup.
- `http_csv` — row filter; latest period by parsed order
(`web_fetcher/periods.py`), mixed formats refused unless `period_format`
is set; without `period_column` the last matching row, stated in `note`.
- `xlsx_wide` — one column per period, stdlib XLSX reader, same period rule;
skips newer periods without a value and says so in `note`.
- `manual` — always `not_found` with a note.
- `http_csv`/`xlsx_wide` return non-numeric values as `not_found` unless
`value_type: string`.
- CLI `python3 -m web_fetcher fetch specs.json [--cache | --replay] [--out] [--only]`
emitting JSONL; exit code 1 if any observation is `error`. Python API
`run_spec`, `run_specs`, `fetch_bytes`.
- 18 offline unit tests plus an opt-in live smoke test (`WEB_FETCHER_LIVE=1`),
last passed 2026-10-19.
- Reuse-surface capability record `capability.infotech.provenance-fetch`
(`registry/`), vector D2 / A3 / C2 / R2.
## Out of Scope
- Crawling, scraping behind logins, JavaScript-rendered pages
(use `capability.infotech.headless-browser`).
- LLM-based extraction or estimation of missing values.
- Scheduling — activity-core owns *when*.
- Execution orchestration — rein-aharness owns *how it runs*.
- Storing or analysing fetched data; that belongs to the consuming research repo.
- Authentication, pagination, third-party runtime dependencies.
## Current State
- Release v0.2.0 (2026-10-19), tagged on Forgejo and pip-installable from the
tag; ~600 lines of Python. See `CHANGELOG.md`.
- Consumer: assembly-economics reality checkpoints (`checkpoints/run_checkpoint.py`).
All 31 of its specs give the same results under 0.1.0 and 0.2.0. It still
reads a checkout via `WEB_FETCHER_PATH` rather than the tag
(`WEBFETCH-WP-0003-T03`).
- Running inside rein-aharness is plausible (stdlib only) but unverified.
- Licence: Target Revenue Source License V1C1 (org-wide preliminary licence).
- CI: Forgejo Actions runs the offline tests on Python 3.10 and 3.13.
## Getting Oriented
- Start with: `INTENT.md`, then `README.md` for spec fields and usage.
- Agent instructions and dev commands: `AGENTS.md`
- Capability record: `registry/capabilities/`
- Workplans: `workplans/`