Add custom ESLint rule scaffolding for Rig (#125)

Author: Copilot

.github/workflows/ci.yml

@@ -22,6 +22,9 @@ jobs:
       - name: Typecheck
         run: npm run typecheck
 
+      - name: Lint
+        run: npm run lint
+
       - name: Test
         run: npm test
 

.github/workflows/daily-rig-task-generator.lock.yml

@@ -229,6 +229,12 @@ Emit a `create-issue` safe output with:
   Identify API patterns that were awkward, frequently confused, or required extra
   boilerplate that a helper could eliminate.
 
+  ### Candidate lint rules
+  For repeated code patterns that confused the model, propose a focused lint rule.
+  Include the proposed rule name, invalid and valid examples, why the pattern is
+  model-confusing, and whether a safe autofix is possible. Do not suggest a rule
+  for a one-off mistake or an issue already caught by the current linter.
+
   ### Documentation gaps
   Note anything in SKILL.md or the references that was underdocumented, missing an
   example, or frequently led to wrong usage.

.github/workflows/daily-rig-task-generator.md

@@ -5,6 +5,7 @@
   "exports": {
     ".": "./skills/rig/rig.ts",
     "./addons": "./skills/rig/addons.ts",
+    "./eslint": "./skills/rig/eslint/index.js",
     "./engines/anthropic": "./skills/rig/engines/anthropic.ts",
     "./engines/codex": "./skills/rig/engines/codex.ts",
     "./engines/gemini": "./skills/rig/engines/gemini.ts",
@@ -15,6 +16,7 @@
     "test:integration": "vitest run scripts/haiku.integration.test.ts",
     "sample": "vitest run scripts/run-sample.test.ts",
     "sample:run": "node skills/rig/rig.ts",
+    "lint": "node skills/rig/eslint/lint.js .",
     "typecheck": "tsc --noEmit"
   },
   "devDependencies": {

package.json

@@ -117,13 +117,20 @@ Typecheck without executing:
 cat program.ts | node skills/rig/rig.ts --typecheck
 ```
 
+Lint a generated program before running it:
+
+```bash
+node skills/rig/eslint/lint.js program.ts
+```
+
 Run inline input or a program file with `node skills/rig/rig.ts`; add `--server` to start the Copilot server. Assume Node.js 24, prefer native APIs, and use `google/zx` for shell-style TypeScript automation.
 
 ## Final checks
 
 - Known context uses `p.*`; true runtime data uses `input`.
 - Important outputs are explicitly typed and constrained.
 - Every helper and import uses the current `rig` or `rig/addons` API.
+- Generated TypeScript passes `node skills/rig/eslint/lint.js <program.ts>` and typechecking.
 - Every subagent is named, reachable, and narrowly scoped.
 - Snippets have one default export and no `console.log`.
 - No deprecated hooks or compatibility layers were introduced.
@@ -136,4 +143,5 @@ Read only the reference needed for the current task:
 - [Agent API and schemas](references/agent-api.md) — spec fields, schema overloads, tools, and call-time options.
 - [Prompt intents](references/prompt-intents.md) — helper semantics, writes, dynamic paths, and failures.
 - [Composition and addons](references/composition.md) — subagents, coordinator patterns, repair, and addon lifecycle.
+- [Linting](references/linting.md) — custom Rig ESLint rules, fixes, and rule scaffolding.
 - [Running and engines](references/runtime.md) — inline/file launch modes, typechecking, stdin coercion, and SDK adapters.

skills/rig/SKILL.md

@@ -0,0 +1,10 @@
+import noObjectLiteralRecord from "./rules/no-object-literal-record.js";
+
+export default {
+  meta: {
+    name: "rig",
+  },
+  rules: {
+    "no-object-literal-record": noObjectLiteralRecord,
+  },
+};

skills/rig/eslint/index.js

@@ -0,0 +1,166 @@
+#!/usr/bin/env node
+
+import { readFile, readdir, writeFile } from "node:fs/promises";
+import { extname, resolve } from "node:path";
+import { pathToFileURL } from "node:url";
+
+const methods = new Set(["record", "nonEmptyObject"]);
+const ignoredDirectories = new Set([".git", "node_modules"]);
+
+function tokenize(source) {
+  const tokens = [];
+  let index = 0;
+
+  while (index < source.length) {
+    const start = index;
+    const char = source[index];
+    const next = source[index + 1];
+
+    if (/\s/.test(char)) {
+      index += 1;
+    } else if (char === "/" && next === "/") {
+      index = source.indexOf("\n", index + 2);
+      if (index === -1) break;
+    } else if (char === "/" && next === "*") {
+      index = source.indexOf("*/", index + 2);
+      index = index === -1 ? source.length : index + 2;
+    } else if (char === "'" || char === "\"" || char === "`") {
+      const quote = char;
+      index += 1;
+      while (index < source.length) {
+        if (source[index] === "\\") {
+          index += 2;
+        } else if (source[index] === quote) {
+          index += 1;
+          break;
+        } else {
+          index += 1;
+        }
+      }
+    } else if (/[A-Za-z_$]/.test(char)) {
+      index += 1;
+      while (index < source.length && /[\w$]/.test(source[index])) index += 1;
+      tokens.push({ value: source.slice(start, index), start, end: index });
+    } else {
+      index += 1;
+      tokens.push({ value: char, start, end: index });
+    }
+  }
+
+  return tokens;
+}
+
+function closingBrace(tokens, openingIndex) {
+  let depth = 0;
+  for (let index = openingIndex; index < tokens.length; index += 1) {
+    if (tokens[index].value === "{") depth += 1;
+    if (tokens[index].value === "}") depth -= 1;
+    if (depth === 0) return index;
+  }
+  return undefined;
+}
+
+export function lintSource(source) {
+  const tokens = tokenize(source);
+  const problems = [];
+
+  for (let index = 0; index <= tokens.length - 5; index += 1) {
+    const [schema, dot, method, openCall] = tokens.slice(index, index + 4);
+    if (
+      tokens[index - 1]?.value === "."
+      || schema.value !== "s"
+      || dot.value !== "."
+      || !methods.has(method.value)
+      || openCall.value !== "("
+    ) {
+      continue;
+    }
+
+    let objectIndex = index + 4;
+    while (tokens[objectIndex]?.value === "(") objectIndex += 1;
+    const object = tokens[objectIndex];
+    if (object?.value !== "{") continue;
+
+    const closingIndex = closingBrace(tokens, objectIndex);
+    const wrapperCount = objectIndex - (index + 4);
+    const wrappersClose = Array.from(
+      { length: wrapperCount },
+      (_, offset) => tokens[(closingIndex ?? tokens.length) + offset + 1]?.value,
+    ).every((value) => value === ")");
+    if (closingIndex !== undefined && wrappersClose) {
+      problems.push({
+        start: object.start,
+        end: tokens[closingIndex].end,
+        message: `Wrap object-valued record fields with s.object(...).`,
+      });
+    }
+  }
+
+  return problems;
+}
+
+export function fixSource(source, problems = lintSource(source)) {
+  let fixed = source;
+  const edits = problems
+    .flatMap(({ start, end }) => [
+      { index: start, text: "s.object(" },
+      { index: end, text: ")" },
+    ])
+    .sort((left, right) => right.index - left.index);
+  for (const edit of edits) {
+    fixed = `${fixed.slice(0, edit.index)}${edit.text}${fixed.slice(edit.index)}`;
+  }
+  return fixed;
+}
+
+async function sourceFiles(paths) {
+  const files = [];
+  for (const path of paths) {
+    const entries = await readdir(path, { withFileTypes: true }).catch(() => undefined);
+    if (!entries) {
+      if (extname(path) === ".ts") files.push(path);
+      continue;
+    }
+    for (const entry of entries) {
+      if (entry.isDirectory() && ignoredDirectories.has(entry.name)) continue;
+      const child = resolve(path, entry.name);
+      if (entry.isDirectory()) files.push(...await sourceFiles([child]));
+      else if (extname(entry.name) === ".ts") files.push(child);
+    }
+  }
+  return files;
+}
+
+async function main(argv) {
+  const fix = argv.includes("--fix");
+  const paths = argv.filter((arg) => arg !== "--fix").map((path) => resolve(path));
+  if (paths.length === 0) {
+    throw new Error("Usage: node skills/rig/eslint/lint.js [--fix] <file-or-directory> [...]");
+  }
+
+  let failures = 0;
+  for (const file of await sourceFiles(paths)) {
+    const source = await readFile(file, "utf8");
+    const problems = lintSource(source);
+    if (problems.length === 0) continue;
+    if (fix) {
+      await writeFile(file, fixSource(source, problems));
+      continue;
+    }
+    failures += problems.length;
+    for (const problem of problems) {
+      const line = source.slice(0, problem.start).split("\n").length;
+      console.error(`${file}:${line}: ${problem.message}`);
+    }
+  }
+
+  if (failures > 0) process.exitCode = 1;
+}
+
+const isMain = process.argv[1] && pathToFileURL(resolve(process.argv[1])).href === import.meta.url;
+if (isMain) {
+  main(process.argv.slice(2)).catch((error) => {
+    console.error(error.message);
+    process.exitCode = 1;
+  });
+}

skills/rig/eslint/lint.js

@@ -0,0 +1,48 @@
+export default {
+  meta: {
+    type: "problem",
+    docs: {
+      description: "Require object-valued record schemas to use s.object",
+    },
+    fixable: "code",
+    schema: [],
+    messages: {
+      wrapObject: "Wrap object-valued record fields with {{schema}}.object(...).",
+    },
+  },
+  create(context) {
+    const sourceCode = context.sourceCode;
+
+    return {
+      CallExpression(node) {
+        const { callee } = node;
+        if (
+          callee.type !== "MemberExpression"
+          || callee.computed
+          || callee.object.type !== "Identifier"
+          || callee.object.name !== "s"
+          || callee.property.type !== "Identifier"
+          || !["record", "nonEmptyObject"].includes(callee.property.name)
+        ) {
+          return;
+        }
+
+        const value = node.arguments[0];
+        if (!value || value.type !== "ObjectExpression") {
+          return;
+        }
+
+        context.report({
+          node: value,
+          messageId: "wrapObject",
+          data: {
+            schema: callee.object.name,
+          },
+          fix(fixer) {
+            return fixer.replaceText(value, `${callee.object.name}.object(${sourceCode.getText(value)})`);
+          },
+        });
+      },
+    };
+  },
+};

skills/rig/eslint/rules/no-object-literal-record.js

@@ -0,0 +1,35 @@
+# Linting Rig programs
+
+Rig includes a dependency-free linter in the skill folder and exports an ESLint plugin from `rig/eslint`.
+
+Run the linter after generating or changing a Rig program:
+
+```bash
+node skills/rig/eslint/lint.js path/to/program.ts
+```
+
+Use `--fix` to apply safe fixes:
+
+```bash
+node skills/rig/eslint/lint.js --fix path/to/program.ts
+```
+
+## Rules
+
+### `rig/no-object-literal-record`
+
+An `s.record` or `s.nonEmptyObject` value must be a schema. Wrap object fields with `s.object`:
+
+```ts
+// Invalid
+s.record({ status: s.string })
+
+// Valid
+s.record(s.object({ status: s.string }))
+```
+
+The rule fixes the invalid form automatically.
+
+## Adding rules
+
+Put rule implementations in `skills/rig/eslint/rules/`, export them from `skills/rig/eslint/index.js`, add the equivalent skill-local check to `skills/rig/eslint/lint.js`, and cover both in `src/eslint-rules.test.js`.

skills/rig/references/linting.md

@@ -0,0 +1,60 @@
+import { describe, expect, it } from "vitest";
+import { fixSource, lintSource } from "../skills/rig/eslint/lint.js";
+import rule from "../skills/rig/eslint/rules/no-object-literal-record.js";
+
+describe("no-object-literal-record", () => {
+  it.each([
+    "const output = s.record(s.object({ count: s.number }));",
+    "const output = s.nonEmptyObject(s.object({ count: s.number }));",
+    "const output = s.record(s.string);",
+    "const output = other.record({ count: s.number });",
+    "const output = config.s.record({ count: s.number });",
+    "const text = 's.record({ count: s.number })';",
+  ])("accepts %s", (source) => {
+    expect(lintSource(source)).toEqual([]);
+  });
+
+  it.each([
+    [
+      "const output = s.record({ count: s.number });",
+      "const output = s.record(s.object({ count: s.number }));",
+    ],
+    [
+      "const output = s.nonEmptyObject(/* value */ { count: s.number });",
+      "const output = s.nonEmptyObject(/* value */ s.object({ count: s.number }));",
+    ],
+    [
+      "const output = s.record(({ count: s.number }));",
+      "const output = s.record((s.object({ count: s.number })));",
+    ],
+  ])("fixes %s", (source, expected) => {
+    const problems = lintSource(source);
+    expect(problems).toHaveLength(1);
+    expect(fixSource(source, problems)).toBe(expected);
+  });
+
+  it("keeps the ESLint rule aligned", () => {
+    const reports = [];
+    const object = { type: "ObjectExpression" };
+    const visitor = rule.create({
+      sourceCode: { getText: () => "{ count: s.number }" },
+      report: (problem) => reports.push(problem),
+    });
+
+    visitor.CallExpression({
+      type: "CallExpression",
+      callee: {
+        type: "MemberExpression",
+        computed: false,
+        object: { type: "Identifier", name: "s" },
+        property: { type: "Identifier", name: "record" },
+      },
+      arguments: [object],
+    });
+
+    expect(reports).toHaveLength(1);
+    expect(reports[0].messageId).toBe("wrapObject");
+    expect(reports[0].fix({ replaceText: (_node, text) => text }))
+      .toBe("s.object({ count: s.number })");
+  });
+});