Required argument aware flag validation
Skill ychampion/cskill-agents/agents/codex/skills/required-argument-aware-flag-validation
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What its author says it does
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Walk command tokens while inspecting attached/inline arguments so validators never skip missing or dangerous flag values.
SKILL.md
2.1 KB, 405 tokens by cl100k_base, as published. Nobody here has run it
SKILL: Required Argument Aware Flag Validation
Domain: validator
Trigger: Apply this whenever flag validation cannot rely on shell parsers and must check --flag=value, combined short bundles, and missing arguments explicitly.
Source Pattern: Distilled from reviewed tool execution, streaming, persistence, and output-budget implementations.
Core Method
Iterate over tokens after the command verb, treat -- according to whether the tool respects it, then inspect each -flag/--flag by looking it up in the declarative config. Handle inline values (-E=), attached numeric args (-A20), and bundles of non-arg flags carefully: reject unknown flags, ensure required arguments exist, and forbid bundles that include arg-taking options. Use typed helpers (validate flag argument) to keep regex/number checks centralized.
Key Rules
- Never assume an inline assignment contains a value;
--flag=must be validated as empty input, not allowed to silently consume the next token. - For launcher commands such as
xargs, stop validating wrapper flags once parsing has switched to the downstream command. - Reject combined short flags if any member expects an argument; allow only
none-type flags in bundles to avoid parser differentials. - Guard string arguments from starting with
-unless the flag explicitly allows it (e.g.,git --sort -version:refname).
Example Application
Implement this in a shell command policy layer by validating the tokenized command against declarative flag metadata before execution. That ensures commands containing -S, --diff-filter, or --flag=value cannot bypass read-only guardrails through parser edge cases.
Anti-Patterns (What NOT to do)
- Do not treat
-FLAG=valuethe same as-FLAG value; the attached format still needs its own validation rules. - Do not skip the empty-inline-value check for
-FLAG=; otherwise attackers can bypass restrictions by hiding invalid input behind=.