typos/docs/about.md
2019-07-03 19:22:36 -06:00

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# About `typos`
## Design Requirements
Spell checks source code:
- Requires special word-splitting logic to handle situations like hex (`0xDEADBEEF`), `c\nescapes`, `snake_case`, `CamelCase`, `SCREAMING_CASE`, and maybe `arrow-case`.
- Each programming language has its own quirks, like abbreviations, lack of word separator (`copysign`), etc
- Backwards compatibility might require keeping misspelled words.
- Case for proper nouns is irrelevant.
Checking for errors in a CI:
- No false-positives.
- On spelling errors, sets the exit code to fail the CI.
Quick feedback and resolution for developer:
- Fix errors for the user.
- Integration into other programs, like editors:
- `fork`: easy to call into and provides a stable API, including output format
- linking: either in the language of choice or bindings can be made to language of choice.
## Design Trade Offs
### typos uses a blacklist
Blacklist: Known typos that map to their corresponding word
- Ignores unknown typos
- Ignores typos that follow c-escapes if they aren't handled correctly
Whitelist: A confidence rating is given for how close a word is to one in the whitelist
- Sensitive to false positives due to hex numbers and c-escapes
- Traditional spell checkers use a whitelist.
## Related Spell Checkers
| | typos | [scspell3k] | [bloom42/misspell][misspell-rs] | [client9/misspell][misspell-go] |
|---------------|-----------------------|-------------|---------------------------------|---------------------------------|
| "Runtime" | Rust ([#18][def-18]) | Python | Rust | None |
| Dictionary | Blacklist | Whitelist | Blacklist | Blacklist |
| Custom Dict | No ([#9][def-9]) | Yes | No | ? |
| Per-Lang Dict | No ([#14][def-14]) | Yes | No | ? |
| CamelCase | Yes | Yes | No | ? |
| snake_case | Yes | Yes | No | ? |
| Ignore Hex | No ([#19][def-19]) | Yes | No | ? |
| C-Escapes | No ([#20][def-3]) | Yes | No | ? |
| Encodings | UTF-8 ([#17][def-17]) | Auto | UTF-8 | ? |
| API | Rust / [JSON Lines] | None | Rust | ? |
| License | MIT | Apache | GPLv2 | AGPL | MIT |
[JSON Lines]: http://jsonlines.org/
[scspell3k]: https://github.com/myint/scspell
[misspell-rs]: https://gitlab.com/bloom42/misspell
[misspell-go]: https://github.com/client9/misspell
[def-9]: https://github.com/epage/typos/issues/9
[def-14]: https://github.com/epage/typos/issues/14
[def-17]: https://github.com/epage/typos/issues/17
[def-18]: https://github.com/epage/typos/issues/18
[def-19]: https://github.com/epage/typos/issues/19
[def-3]: https://github.com/epage/typos/issues/3