Jev Directory

Code review

Flag hidden side effects

Identify functions whose names and contracts hide observable changes.

NoulOriginal exampleSource reviewedNot live-tested

01 The question

hidden_effect noul

Does this function change observable state in a way that is not apparent from its name or supplied contract?

true
It writes external or shared state, performs I/O, or mutates an argument without making that behavior clear.
false
It is read-only, or its observable changes are clearly part of the supplied contract.

Copy includes the complete instructions, criteria, usage notes, and attribution.

02 Input

A complete function, relevant surrounding state, and its documented contract.

Illustrative input · JSON
{
  "code": "let views = 0;\nfunction getPrice(product) {\n  views += 1;\n  return product.price;\n}",
  "contract": "getPrice returns the product price. No side effects are documented."
}

03 Answer & policy

A Noul probability that the function has an undisclosed observable side effect.

Your code decides what happens next.

Use a high probability to start a review conversation, not to automatically reject code. The example reports the probability without choosing a universal cutoff.

04 Use it in your code

Node.js 24 · TypeSafe SDK 0.6.0 · Set TYPESAFE_API_KEY in your environment. Run on your server; API calls incur provider charges.

decision.ts · TypeScript
import { noul, TypeSafeClient, type JsonValue } from "@typesafe-ai/sdk";

// Illustrative input, not a recorded model test.
const state: JsonValue = {
  "code": "let views = 0;\nfunction getPrice(product) {\n  views += 1;\n  return product.price;\n}",
  "contract": "getPrice returns the product price. No side effects are documented."
};
const client = new TypeSafeClient();
try {
  const response = await client.systemOne({
    model: "jev-latest",
    state,
    questions: {
      hidden_effect: noul(
        "Does this function change observable state in a way that is not apparent from its name or supplied contract?",
        {
          "true": "It writes external or shared state, performs I/O, or mutates an argument without making that behavior clear.",
          "false": "It is read-only, or its observable changes are clearly part of the supplied contract."
        }
      )
    },
  });

  console.log({ hiddenEffectProbability: response.answers.hidden_effect.noul, action: "human_review" });
} catch (error) {
  console.error("Decision unavailable; use your fallback or human review.", error);
  process.exitCode = 1;
}
Download .ts ↓SDK setup ↗Copy and download include license notices.

The wrapper and example input are provided by Jev Directory. Checked against SDK types; no live model call was made. Pin a model version before evaluating production behavior.

Before you adapt it

  • Missing caller or contract context can make an intentional effect look unexpected.
  • This is not Jeff’s built-in rule or a claim of CLI compatibility.
More about the original project or pattern

What it does

Jeff checks files against twenty named semantic rules. The catalog covers concerns such as unclear responsibility, hidden side effects, weak error context, unnecessary complexity, duplicated domain knowledge, fragile control flow, boundary separation, and testability.

What you can reuse

The strongest reusable idea is the rule contract: a stable identifier, a narrow question, and a CI-compatible outcome. Jeff separates a conclusive violation from an inconclusive or provider error through distinct exit codes, which is valuable whenever probabilistic judgments enter an automated check.

How it fits

Source files and a fixed rule catalog become typed checks. The CLI can print a human-readable report or JSON for automation. Jev performs semantic judgment; the process controls input discovery, result formatting, and exit behavior.

Setup and compatibility

The documented interface is jeff check, with optional JSON output and cache control. Authentication uses a TypeSafe API key from the environment or the operating system keyring. A custom TypeSafe-compatible base URL can be configured for testing.

Limitations

The visible repository did not show a license at review time, so this entry links to the implementation without republishing its code. The README documents a built-in rule set; it does not establish a portable third-party rule format. Jev Directory has not run the CLI.

Sources

Primary source: Jeff repository.