[timothyanderson096-ocdealcheck]

Fixes #447. Implements the Excel comparison report requested in #443.

cancompare --output changes.xlsx old.dbc new.dbc

Add --output / -o and dump_result_xlsx() to write a filterable report with Object, Property, Change, Old value and New value columns. The report traverses the existing CompareResult tree and respects the current comment, attribute and value-table filters. It adds no new comparison rules. Existing console output remains available.

Populate one-sided change values for transmitters, receivers, definitions and global value tables so the report identifies the actual added/removed value. Their console output is unchanged. Legacy value-table/signal-group change pairs are also handled. Named global tables and definitions retain their identity, and custom attributes can share structural node names without being mistaken for those objects. Added/removed named objects show their names; the report is not a full database export.

All cells are literal text, preserving Unicode, decimal precision and strings beginning with =. The report is written before the existing console formatter mutates string values. Values over Excel's 32767-character cell limit fail before saving; equal databases produce headers only. Excel dependencies remain optional, with an actionable CLI error when absent. --frames and non-XLSX output paths are rejected explicitly.

Validation on Linux, Python 3.13.16, based on development 06e852d:

• tox -e gh: 397 passed, 1 skipped, including 18 report cases.
• Wheel and source archive build, plus twine check --strict: passed.
• Console comparison without openpyxl: passed.
• Console output matched unmodified development for the change/addition/removal fixture.
• git diff --check: passed.

Windows/macOS and other Python-version jobs remain for upstream CI. Prepared and checked with AI assistance.

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Timothy Anderson — Spotted Ridge Engineering / OC Labs
GDN — Global Decision Network
timothyanderson096@gmail.com · Engineering evidence