typos/docs/about.md

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

See also benchmarks.

	typos	bloom42/misspell	client9/misspell	codespell	scspell3k
Runtime	-	-	-	Python	Python
Dictionary	Blacklist	Blacklist	Blacklist	Blacklist	Whitelist
Custom Dict	Yes	No	?	Yes	Yes
Per-Lang Dict	No (#14)	No	?	No	Yes
CamelCase	Yes	No	?	No	Yes
snake_case	Yes	No	?	No	Yes
Ignore Hex	Yes	No	?	No	Yes
C-Escapes	No (#20)	No	?	No	Yes
Encodings	UTF-8 (#17)	UTF-8	?	Auto	Auto
Whole-project	Yes	Yes	Yes	Yes	No
Ignores hidden	Yes	Yes	?	Yes	No
Respect gitignore	Yes	Yes	?	No	No
Checks filenames	Yes	No	?	Yes	No
Status via exit code	Yes	No	Yes	Yes	Yes
API	Rust / JSON Lines	Rust	?	Python	None
License	MIT or Apache	AGPL	MIT	GPLv2	GPLv2