style-tripwire

1import type { EngineInterface, Register } from 'claude-code'
2
3type Rule = {
4  name: string
5  pattern: string
6  flags?: string
7  message: string
8  files?: string
9  commits?: boolean
10  action?: 'block' | 'warn'
11}
12type Config = { defaults?: boolean; rules?: Rule[] }
13type Compiled = Rule & { regex: RegExp; fileRegex?: RegExp }
14type Hit = { rule: Compiled; line: string }
15
16const NAME = 'style-tripwire'
17
18const DEFAULT_RULES: Rule[] = [
19  {
20    name: 'merge-conflict-marker',
21    pattern: '^(<{7}|>{7})( |$)',
22    message: 'Resolve the merge conflict instead of writing its markers.',
23  },
24]
25
26const readConfig = async ($: EngineInterface, path: string): Promise<Config> => {
27  if (!(await $.fs.exists(path))) return {}
28  try {
29    return JSON.parse(await $.fs.read(path)) as Config
30  } catch {
31    $.ui.toast(`${NAME}: ${path} is not valid JSON, so it was ignored`)
32    return {}
33  }
34}
35
36const compile = ($: EngineInterface, rule: Rule): Compiled[] => {
37  try {
38    return [{
39      ...rule,
40      regex: new RegExp(rule.pattern, (rule.flags ?? '').replace('g', '')),
41      fileRegex: rule.files === undefined ? undefined : new RegExp(rule.files),
42    }]
43  } catch {
44    $.ui.toast(`${NAME}: rule "${rule.name}" has an invalid pattern, so it was skipped`)
45    return []
46  }
47}
48
49const loadRules = async ($: EngineInterface): Promise<Compiled[]> => {
50  const home = await $.env.get('HOME')
51  const global = home === undefined ? {} : await readConfig($, `${home}/.claude/${NAME}.json`)
52  const project = await readConfig($, `.claude/${NAME}.json`)
53  const defaults = project.defaults ?? global.defaults ?? true
54  const rules = [...(defaults ? DEFAULT_RULES : []), ...(global.rules ?? []), ...(project.rules ?? [])]
55
56  return rules.flatMap(rule => compile($, rule))
57}
58
59const addedLines = (before: string, after: string) => {
60  const existing = new Set(before.split('\n'))
61  return after.split('\n').filter(line => !existing.has(line))
62}
63
64const findHits = (rules: Compiled[], lines: string[]): Hit[] =>
65  rules.flatMap(rule => {
66    const line = lines.find(candidate => rule.regex.test(candidate))
67    return line === undefined ? [] : [{ rule, line: line.trim().slice(0, 120) }]
68  })
69
70const describe = (hits: Hit[]) =>
71  hits.map(({ rule, line }) => `- ${rule.name}: ${rule.message}\n  in: ${line}`).join('\n')
72
73
74export const register: Register = on => {
75  on('tool.call', async ($, e, next) => {
76    let lines: string[] | undefined
77    let path: string | undefined
78
79    if (e.tool === 'Edit') {
80      path = e.file_path
81      lines = addedLines(e.old_string, e.new_string)
82    } else if (e.tool === 'Write') {
83      path = e.file_path
84      const before = (await $.fs.exists(path)) ? await $.fs.read(path) : ''
85      lines = addedLines(before, e.content)
86    } else if (e.tool === 'Bash' && /\bgit\s+commit\b/.test(e.command)) {
87      lines = e.command.split('\n')
88    }
89
90    if (lines === undefined) return next(e)
91
92    const rules = (await loadRules($)).filter(rule =>
93      path === undefined ? rule.commits === true : rule.fileRegex === undefined || rule.fileRegex.test(path),
94    )
95    const hits = findHits(rules, lines)
96    const blocking = hits.filter(hit => (hit.rule.action ?? 'block') === 'block')
97
98    if (blocking.length > 0) {
99      return { deny: `${NAME}: this change trips the house style rules. Fix it and try again.\n${describe(blocking)}` }
100    }
101    if (hits.length === 0) return next(e)
102
103    $.ui.toast(`${NAME}: ${hits.map(hit => hit.rule.name).join(', ')}`)
104    const ran = await next(e)
105    if (ran.deny !== undefined) return ran
106
107    return { ...ran, context: [...(ran.context ?? []), `${NAME} warnings, worth fixing:\n${describe(hits)}`] }
108  }).catch(($, e, next) => {
109    $.ui.toast(`${NAME}: the check failed, so this call went through unchecked`)
110    return next(e)
111  })
112}
113