feat: stable virtual printer ids — optional explicit id + safe slug — closes #42

[szrudi]

Closes #42. Stacked under #39 (per-printer settings); no version bump — ships in the single v1.8.0 that #39 cuts.

Why

Virtual ids were derived from the display name with a minimal sanitizer (spaces/parens only) and no uniqueness check (virtual_printer.py, config.py):

• distinct names could collide onto one id → shared settings + the second printer shadowed at print time;
• path-hostile characters (notably /) survived into the /api/printers/<path:printer_id>/settings route;
• the id changed whenever the display name was edited → saved settings orphaned.

What

• Optional explicit id in VIRTUAL_PRINTERS entries → virtual:<id>: a stable, URL-safe identity decoupled from the display name (the virtual analog of Key per-printer settings by serial number, not the unstable USB bus/address id #40's serial). Renaming name no longer orphans settings.
• Path-safe slug fallback when no id: collapse non-word runs to _, keep Unicode letters (they %-encode fine), fall back to printer for an empty result.
• Config-load validation: reject a non-URL-safe explicit id ([A-Za-z0-9_-]); skip an entry whose id collides with an earlier one — both warn.
• VirtualPrinter.from_config: single construction path, so the resolved id is consistent across listing, lookup, and printing (replaces 4 duplicated constructions).

Compatibility

Existing id-less configs keep working via the slug. The slug differs from the old sanitizer only for path-hostile names (/, ., emoji) — acceptable, since per-printer settings (#20/#39) aren't released yet, so nothing durable re-keys. Existing tests asserting the old incidental behavior (test_slashes_preserved etc.) updated to the new contract.

Tests

virtual_printer (slug cases, explicit id, from_config), config (explicit id kept, invalid skipped, derived + explicit collisions skipped). Full backend suite green (231); no import cycle from the new config → virtual_printer dependency (smoke imports all modules).

🤖 Generated with Claude Code

[Copilot]

Pull request overview

Adds stable, URL-safe virtual printer identities to prevent id collisions, path-hostile characters in printer ids, and settings orphaning when display names change.

Changes:

• Introduces optional explicit virtual printer id (suffix) plus a safer slug fallback for name-derived ids.
• Validates virtual printer ids at config load time (charset check + collision detection) and skips invalid/colliding entries with warnings.
• Centralizes virtual printer construction via VirtualPrinter.from_config() and updates relevant code paths + tests/docs.

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
server/virtual_printer.py	Adds slug/validation helpers, optional explicit id support, and from_config() constructor.
server/config.py	Validates explicit ids and guards against computed-id collisions during config load.
server/printer_service.py	Uses VirtualPrinter.from_config() to ensure consistent id resolution across listing/lookup/printing.
server/tests/test_virtual_printer.py	Updates id behavior tests (slugging rules, explicit id, from_config).
server/tests/test_config.py	Adds coverage for explicit id retention, invalid id skipping, and collision handling.
README.md	Documents optional id field and collision behavior for VIRTUAL_PRINTERS.
docs/ARCHITECTURE.md	Updates identity model documentation for virtual printers (explicit id + slug fallback).

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[Copilot]

Pull request overview

Copilot reviewed 7 out of 7 changed files in this pull request and generated 1 comment.