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54 lines
2.3 KiB
Markdown
54 lines
2.3 KiB
Markdown
# Design
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## Requirements
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Spell checks source code:
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- Requires special word-splitting logic to handle situations like hex (`0xDEADBEEF`), `c\nescapes`, `snake_case`, `CamelCase`, `SCREAMING_CASE`, and maybe `arrow-case`.
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- Each programming language has its own quirks, like abbreviations, lack of word separator (`copysign`), etc
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- Backwards compatibility might require keeping misspelled words.
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- Case for proper nouns is irrelevant.
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Checking for errors in a CI:
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- No false-positives.
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- On spelling errors, sets the exit code to fail the CI.
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- Machine-independent, repo-specific configuration
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- As compared to layered config with the users system or the command-line
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Quick feedback and resolution for developer:
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- Fix errors for the user.
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- Integration into other programs, like editors:
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- `fork`: easy to call into and provides a stable API, including output format
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- linking: either in the language of choice or bindings can be made to language of choice.
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## Trade Offs
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### Corrections vs Dictionaries
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Corrections: Known misspellings that map to their corresponding dictionary word
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- Ignores unknown typos
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- Ignores typos that follow c-escapes if they aren't handled correctly
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- Good for unassisted automated correcting
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- Fast, can quickly run across large code bases
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Dictionary: A confidence rating is given for how close a word is to one in a dictionary
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- Sensitive to false positives due to hex numbers and c-escapes
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- Used in word processors and other traditional spell checking applications
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- Good when there is a UI to let the user know and override any decisions
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## Identifiers and Words
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With a focus on spell checking source code, most text will be in the form of
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identifiers that are made up of words conjoined via `snake_case`, `CamelCase`,
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etc. A typo at the word level might not be a typo as part of
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an identifier, so identifiers get checked and, if not in a dictionary, will
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then be split into words to be checked.
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Identifiers are defined using
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[unicode's `XID_Continue`](https://www.unicode.org/reports/tr31/#Table_Lexical_Classes_for_Identifiers)
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which includes `[a-zA-Z0-9_]`.
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Words are split from identifiers on case changes as well as breaks in
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`[a-zA-Z]` with a special case to handle acronyms. For example,
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`First10HTMLTokens` would be split as `first`, `html`, `tokens`.
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To see this in action, run `typos --identifiers` or `typos --words`.
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