Function isSubstitutionCommand

src/tools/BashTool/sedValidation.ts:142–238

* Pattern 2: Check if this is a substitution command * Allows: sed 's/pattern/replacement/flags' where flags are only: g, p, i, I, m, M, 1-9 * When allowFileWrites is true, allows -i flag and file arguments for in-place editing * When allowFileWrites is false (default), requires stdout-only (no f

(
  command: string,
  expressions: string[],
  hasFileArguments: boolean,
  options?: { allowFileWrites?: boolean },
)

 * @internal Exported for testing
 */
function isSubstitutionCommand(
  command: string,
  expressions: string[],
  hasFileArguments: boolean,
  options?: { allowFileWrites?: boolean },
): boolean {
  const allowFileWrites = options?.allowFileWrites ?? false

  // When not allowing file writes, must NOT have file arguments
  if (!allowFileWrites && hasFileArguments) {
    return false
  }

  const sedMatch = command.match(/^\s*sed\s+/)
  if (!sedMatch) return false

  const withoutSed = command.slice(sedMatch[0].length)
  const parseResult = tryParseShellCommand(withoutSed)
  if (!parseResult.success) return false
  const parsed = parseResult.tokens

  // Extract all flags
  const flags: string[] = []
  for (const arg of parsed) {
    if (typeof arg === 'string' && arg.startsWith('-') && arg !== '--') {
      flags.push(arg)
    }
  }

  // Validate flags based on mode
  // Base allowed flags for both modes
  const allowedFlags = ['-E', '--regexp-extended', '-r', '--posix']

  // When allowing file writes, also permit -i and --in-place
  if (allowFileWrites) {
    allowedFlags.push('-i', '--in-place')
  }

  if (!validateFlagsAgainstAllowlist(flags, allowedFlags)) {
    return false
  }

  // Must have exactly one expression
  if (expressions.length !== 1) {
    return false
  }

  const expr = expressions[0]!.trim()

  // STRICT ALLOWLIST: Must be exactly a substitution command starting with 's'
  // This rejects standalone commands like 'e', 'w file', etc.
  if (!expr.startsWith('s')) {
    return false
  }

  // Parse substitution: s/pattern/replacement/flags
  // Only allow / as delimiter (strict)
  const substitutionMatch = expr.match(/^s\/(.*?)$/)