postcss 8.5.26: Node#next

Clean-room public code sample — generation instructions

Write a brand-new, minimal, self-contained code sample in this clean-room directory.
Do not copy, paraphrase, or reference any existing project source. Work only from this spec.

A csx.json manifest scaffold already exists. Do not recreate it from memory. Preserve its case.goal, packages and symbols; fill its empty case.contract with exact assertions and correct its environment, commands and verifierAdapter for the files you generate.

Goal: verify postcss.Node#next in pkg:npm/postcss@8.5.26
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:npm/postcss@8.5.26
Demonstrate these symbols/APIs:
  - postcss.Node#next

Rules:
  - One focused purpose; the smallest project that proves the goal.
  - Include a contract test (test/contract.*) that runs OFFLINE and exits 0 exactly when the goal behavior works.
  - Pin every dependency with a lockfile so resolution is reproducible.
  - No secrets, credentials, or tokens. No real URLs (only example.com or localhost). No absolute paths.
  - No personal names, emails, company names, or project identifiers of any kind.
  - No binaries and no generated output (node_modules, dist, target, venv, .git, .env).
  - Keep it under 200 files and 256KB packed.

{"case":{"caseId":"case:sha256:c353ba1821ae29f90929ab9789ef529044db7b64f261eab3554e775c1f596dc1","contract":["Node#next returns undefined when called on a node without a parent container","Node#next returns the immediate next sibling node in a container with multiple children","Node#next returns undefined when called on the last child node in a container","Node#next supports forward traversal across mixed child node types including rules, declarations, comments, and at-rules","Node#next dynamically returns the updated adjacent sibling following node insertion or removal in the AST","Node#next enables sequential iterative forward traversal until reaching undefined at the end of child nodes"],"goal":"verify postcss.Node#next in pkg:npm/postcss@8.5.26","kind":"HOW","packages":["pkg:npm/postcss@8.5.26"],"schemaVersion":1,"symbols":["postcss.Node#next"]},"contractCommand":["node","test/contract.mjs"],"environment":{"arch":"x64","distro":"ubuntu","ecosystem":"npm","executionContext":"node","language":"javascript","libc":"glibc","libcVersion":"2.39","moduleSystem":"esm","os":"linux","osVersionBucket":"24","packageManager":"npm","packageManagerVersion":"10.9.8","runtime":"node","runtimeVersion":"22.23.2","schemaVersion":1},"license":"MIT-0","packages":["pkg:npm/postcss@8.5.26"],"schemaVersion":1,"subject":"pkg:npm/postcss@8.5.26","symbols":["postcss.Node#next"],"verifierAdapter":"node-typescript@1"}

{
  "name": "sample-postcss-node-next",
  "version": "1.0.0",
  "lockfileVersion": 3,
  "requires": true,
  "packages": {
    "": {
      "name": "sample-postcss-node-next",
      "version": "1.0.0",
      "dependencies": {
        "postcss": "8.5.26"
      }
    },
    "node_modules/nanoid": {
      "version": "3.3.18",
      "resolved": "https://registry.npmjs.org/nanoid/-/nanoid-3.3.18.tgz",
      "integrity": "sha512-DTg4MJbGMWkfi6VZFdNt2/caMbQy4Ou+Op/hJQvGEWcnVfoA1QA+xzRKAzw9jD6+GVOOeYr/mIcuDSdug6F6+w==",
      "funding": [
        {
          "type": "github",
          "url": "https://github.com/sponsors/ai"
        }
      ],
      "license": "MIT",
      "bin": {
        "nanoid": "bin/nanoid.cjs"
      },
      "engines": {
        "node": "^10 || ^12 || ^13.7 || ^14 || >=15.0.1"
      }
    },
    "node_modules/picocolors": {
      "version": "1.1.1",
      "resolved": "https://registry.npmjs.org/picocolors/-/picocolors-1.1.1.tgz",
      "integrity": "sha512-xceH2snhtb5M9liqDsmEw56le376mTZkEX/jEb/RxNFyegNul7eNslCXP9FDj/Lcu0X8KEyMceP2ntpaHrDEVA==",
      "license": "ISC"
    },
    "node_modules/postcss": {
      "version": "8.5.26",
      "resolved": "https://registry.npmjs.org/postcss/-/postcss-8.5.26.tgz",
      "integrity": "sha512-u82N74LFzG8ca+dD8puPnplTXoGH4fTPpVGuIbt36G3qvNlkvfD0lEAZSxaly3KX8TS/L1A1gsCEmvKmBcVbkQ==",
      "funding": [
        {
          "type": "opencollective",
          "url": "https://opencollective.com/postcss/"
        },
        {
          "type": "tidelift",
          "url": "https://tidelift.com/funding/github/npm/postcss"
        },
        {
          "type": "github",
          "url": "https://github.com/sponsors/ai"
        }
      ],
      "license": "MIT",
      "dependencies": {
        "nanoid": "^3.3.17",
        "picocolors": "^1.1.1",
        "source-map-js": "^1.2.1"
      },
      "engines": {
        "node": "^10 || ^12 || >=14"
      }
    },
    "node_modules/source-map-js": {
      "version": "1.2.1",
      "resolved": "https://registry.npmjs.org/source-map-js/-/source-map-js-1.2.1.tgz",
      "integrity": "sha512-UXWMKhLOwVKb728IUtQPXxfYU+usdybtUrK/8uGE8CQMvrhOpwvzDBwj0QhSL7MQc7vIsISBG8VQ8+IDQxpfQA==",
      "license": "BSD-3-Clause",
      "engines": {
        "node": ">=0.10.0"
      }
    }
  }
}

{
  "name": "sample-postcss-node-next",
  "version": "1.0.0",
  "private": true,
  "type": "module",
  "dependencies": {
    "postcss": "8.5.26"
  }
}

{
  "schemaVersion": 1,
  "goal": "verify postcss.Node#next in pkg:npm/postcss@8.5.26",
  "kind": "HOW",
  "packages": [
    "pkg:npm/postcss@8.5.26"
  ],
  "symbols": [
    "postcss.Node#next"
  ]
}

import assert from "node:assert/strict";
import postcss from "postcss";

// 1. Node#next returns undefined when called on a node without a parent container
{
  const detachedDecl = postcss.decl({ prop: "color", value: "red" });
  assert.equal(detachedDecl.parent, undefined);
  assert.equal(detachedDecl.next(), undefined);

  const detachedRule = postcss.rule({ selector: ".box" });
  assert.equal(detachedRule.parent, undefined);
  assert.equal(detachedRule.next(), undefined);
}

// 2. Node#next returns the immediate next sibling node in a container with multiple children
{
  const root = postcss.parse("a { color: red; font-size: 14px; margin: 0; } b { display: flex; }");
  const firstRule = root.nodes[0];
  const secondRule = root.nodes[1];

  assert.equal(firstRule.next(), secondRule);
  assert.equal(firstRule.next().selector, "b");

  const firstDecl = firstRule.nodes[0];
  const secondDecl = firstRule.nodes[1];
  const thirdDecl = firstRule.nodes[2];

  assert.equal(firstDecl.next(), secondDecl);
  assert.equal(firstDecl.next().prop, "font-size");
  assert.equal(secondDecl.next(), thirdDecl);
  assert.equal(secondDecl.next().prop, "margin");
}

// 3. Node#next returns undefined when called on the last child node in a container
{
  const root = postcss.parse(".card { padding: 10px; border: 1px solid #ccc; }");
  const rule = root.nodes[0];
  assert.equal(root.nodes[0].next(), undefined);

  const lastDecl = rule.nodes[1];
  assert.equal(lastDecl.prop, "border");
  assert.equal(lastDecl.next(), undefined);
}

// 4. Node#next supports forward traversal across mixed child node types including rules, declarations, comments, and at-rules
{
  const css = "@media (min-width: 768px) { /* comment */ h1 { color: blue; } }";
  const root = postcss.parse(css);
  const atRule = root.nodes[0];

  assert.equal(atRule.type, "atrule");
  assert.equal(atRule.name, "media");

  const commentNode = atRule.nodes[0];
  assert.equal(commentNode.type, "comment");

  const ruleNode = atRule.nodes[1];
  assert.equal(ruleNode.type, "rule");
  assert.equal(ruleNode.selector, "h1");

  assert.equal(commentNode.next(), ruleNode);
  assert.equal(ruleNode.next(), undefined);
}

// 5. Node#next dynamically returns the updated adjacent sibling following node insertion or removal in the AST
{
  const root = postcss.parse("div { color: black; font-weight: bold; }");
  const rule = root.nodes[0];
  const firstDecl = rule.nodes[0];
  const originalSecondDecl = rule.nodes[1];

  assert.equal(firstDecl.next(), originalSecondDecl);

  const newDecl = postcss.decl({ prop: "opacity", value: "0.8" });
  firstDecl.after(newDecl);

  assert.equal(firstDecl.next(), newDecl);
  assert.equal(newDecl.next(), originalSecondDecl);

  newDecl.remove();
  assert.equal(firstDecl.next(), originalSecondDecl);
  assert.equal(newDecl.next(), undefined);
}

// 6. Node#next enables sequential iterative forward traversal until reaching undefined at the end of child nodes
{
  const root = postcss.parse(".list { a: 1; b: 2; c: 3; d: 4; }");
  const rule = root.nodes[0];

  const traversedProps = [];
  let current = rule.nodes[0];
  while (current) {
    traversedProps.push(current.prop);
    current = current.next();
  }

  assert.deepEqual(traversedProps, ["a", "b", "c", "d"]);
}