@webassemblyjs/helper-wasm-section 1.14.1: create, resize, and remove WebAssembly sections in binary buffer

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: create, resize, and remove WebAssembly sections in binary buffer
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:npm/%40webassemblyjs/helper-wasm-section@1.14.1
Demonstrate these symbols/APIs:
  - createEmptySection
  - removeSections
  - resizeSectionByteSize
  - resizeSectionVecSize

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.

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  "requires": true,
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      "license": "MIT"
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      "license": "MIT"
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        "@xtuc/long": "4.2.2"
      }
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      "license": "MIT"
    },
    "node_modules/@webassemblyjs/helper-wasm-section": {
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      "resolved": "https://registry.npmjs.org/@webassemblyjs/helper-wasm-section/-/helper-wasm-section-1.14.1.tgz",
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      "license": "MIT",
      "dependencies": {
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        "@webassemblyjs/wasm-gen": "1.14.1"
      }
    },
    "node_modules/@webassemblyjs/ieee754": {
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      "license": "MIT",
      "dependencies": {
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      }
    },
    "node_modules/@webassemblyjs/leb128": {
      "version": "1.13.2",
      "resolved": "https://registry.npmjs.org/@webassemblyjs/leb128/-/leb128-1.13.2.tgz",
      "integrity": "sha512-Lde1oNoIdzVzdkNEAWZ1dZ5orIbff80YPdHx20mrHwHrVNNTjNr8E3xz9BdpcGqRQbAEa+fkrCb+fRFTl/6sQw==",
      "license": "Apache-2.0",
      "dependencies": {
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      }
    },
    "node_modules/@webassemblyjs/utf8": {
      "version": "1.13.2",
      "resolved": "https://registry.npmjs.org/@webassemblyjs/utf8/-/utf8-1.13.2.tgz",
      "integrity": "sha512-3NQWGjKTASY1xV5m7Hr0iPeXD9+RDobLll3T9d2AO+g3my8xy5peVyjSag4I50mR1bBSN/Ct12lo+R9tJk0NZQ==",
      "license": "MIT"
    },
    "node_modules/@webassemblyjs/wasm-gen": {
      "version": "1.14.1",
      "resolved": "https://registry.npmjs.org/@webassemblyjs/wasm-gen/-/wasm-gen-1.14.1.tgz",
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      "license": "MIT",
      "dependencies": {
        "@webassemblyjs/ast": "1.14.1",
        "@webassemblyjs/helper-wasm-bytecode": "1.13.2",
        "@webassemblyjs/ieee754": "1.13.2",
        "@webassemblyjs/leb128": "1.13.2",
        "@webassemblyjs/utf8": "1.13.2"
      }
    },
    "node_modules/@xtuc/ieee754": {
      "version": "1.2.0",
      "resolved": "https://registry.npmjs.org/@xtuc/ieee754/-/ieee754-1.2.0.tgz",
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      "license": "Apache-2.0"
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}

{
  "name": "sample-webassemblyjs-helper-wasm-section",
  "version": "1.0.0",
  "private": true,
  "type": "module",
  "license": "MIT-0",
  "dependencies": {
    "@webassemblyjs/helper-wasm-section": "1.14.1"
  }
}

{
  "schemaVersion": 1,
  "goal": "create, resize, and remove WebAssembly sections in binary buffer",
  "kind": "HOW",
  "packages": [
    "pkg:npm/%40webassemblyjs/helper-wasm-section@1.14.1"
  ],
  "symbols": [
    "createEmptySection",
    "removeSections",
    "resizeSectionByteSize",
    "resizeSectionVecSize"
  ]
}

import {
  createEmptySection,
  removeSections,
  resizeSectionByteSize,
  resizeSectionVecSize,
} from "@webassemblyjs/helper-wasm-section";

/**
 * Creates an empty AST container suitable for WebAssembly modules with section metadata.
 * @returns {object} WebAssembly Program AST node
 */
export function createEmptyModuleAst() {
  return {
    type: "Program",
    body: [
      {
        type: "Module",
        id: null,
        fields: [],
        metadata: {
          type: "ModuleMetadata",
          sections: [],
        },
      },
    ],
  };
}

/**
 * Inserts an empty section into the WebAssembly binary buffer and AST.
 * @param {object} ast
 * @param {Uint8Array|Buffer} uint8Buffer
 * @param {string} sectionName
 * @returns {{ uint8Buffer: Uint8Array, sectionMetadata: object }}
 */
export function addEmptySection(ast, uint8Buffer, sectionName) {
  return createEmptySection(ast, uint8Buffer, sectionName);
}

/**
 * Removes a section from the AST and deletes its bytes from the buffer.
 * @param {object} ast
 * @param {Uint8Array|Buffer} uint8Buffer
 * @param {string} sectionName
 * @returns {Uint8Array|Buffer}
 */
export function deleteSection(ast, uint8Buffer, sectionName) {
  return removeSections(ast, uint8Buffer, sectionName);
}

/**
 * Resizes the byte size field of a section by deltaBytes.
 * @param {object} ast
 * @param {Uint8Array|Buffer} uint8Buffer
 * @param {string} sectionName
 * @param {number} deltaBytes
 * @returns {Uint8Array|Buffer}
 */
export function adjustSectionByteSize(ast, uint8Buffer, sectionName, deltaBytes) {
  return resizeSectionByteSize(ast, uint8Buffer, sectionName, deltaBytes);
}

/**
 * Resizes the vector element count field of a section by deltaElements.
 * @param {object} ast
 * @param {Uint8Array|Buffer} uint8Buffer
 * @param {string} sectionName
 * @param {number} deltaElements
 * @returns {Uint8Array|Buffer}
 */
export function adjustSectionVecSize(ast, uint8Buffer, sectionName, deltaElements) {
  return resizeSectionVecSize(ast, uint8Buffer, sectionName, deltaElements);
}

export {
  createEmptySection,
  removeSections,
  resizeSectionByteSize,
  resizeSectionVecSize,
};

import assert from "node:assert/strict";
import {
  createEmptyModuleAst,
  addEmptySection,
  deleteSection,
  adjustSectionByteSize,
  adjustSectionVecSize,
  createEmptySection,
  removeSections,
  resizeSectionByteSize,
  resizeSectionVecSize,
} from "../src/index.mjs";

const wasmHeader = Buffer.from([0x00, 0x61, 0x73, 0x6d, 0x01, 0x00, 0x00, 0x00]);

// Contract Assertion 1: createEmptySection inserts a new section into the AST metadata and encodes section bytes in the buffer
{
  const ast = createEmptyModuleAst();
  const { uint8Buffer: buf1, sectionMetadata: meta1 } = addEmptySection(ast, wasmHeader, "type");

  assert.equal(meta1.section, "type");
  assert.equal(meta1.size.value, 1);
  assert.equal(meta1.vectorOfSize.value, 0);
  assert.equal(ast.body[0].metadata.sections.length, 1);
  assert.equal(ast.body[0].metadata.sections[0].section, "type");
  assert.equal(buf1.length, 11);
  assert.equal(buf1[8], 1); // section ID for "type" section
  assert.equal(buf1[9], 1); // section byte size
  assert.equal(buf1[10], 0); // vector size

  const { uint8Buffer: buf2, sectionMetadata: meta2 } = createEmptySection(ast, buf1, "import");
  assert.equal(meta2.section, "import");
  assert.equal(ast.body[0].metadata.sections.length, 2);
  assert.equal(ast.body[0].metadata.sections[1].section, "import");
  assert.equal(buf2.length, 14);
  assert.equal(buf2[11], 2); // section ID for "import" section
}

// Contract Assertion 2: resizeSectionByteSize adjusts the byte length of an existing section in the AST and buffer
{
  const ast = createEmptyModuleAst();
  const { uint8Buffer: buf, sectionMetadata: meta } = createEmptySection(ast, wasmHeader, "type");
  const updatedBuf = adjustSectionByteSize(ast, buf, "type", 4);

  assert.equal(meta.size.value, 5);
  assert.equal(updatedBuf[9], 5);

  const directBuf = resizeSectionByteSize(ast, updatedBuf, "type", -2);
  assert.equal(meta.size.value, 3);
  assert.equal(directBuf[9], 3);
}

// Contract Assertion 3: resizeSectionVecSize updates vector element count in section header and updates buffer
{
  const ast = createEmptyModuleAst();
  const { uint8Buffer: buf, sectionMetadata: meta } = createEmptySection(ast, wasmHeader, "type");
  const updatedBuf = adjustSectionVecSize(ast, buf, "type", 3);

  assert.equal(meta.vectorOfSize.value, 3);
  assert.equal(updatedBuf[10], 3);

  const directBuf = resizeSectionVecSize(ast, updatedBuf, "type", 2);
  assert.equal(meta.vectorOfSize.value, 5);
  assert.equal(directBuf[10], 5);
}

// Contract Assertion 4: removeSections deletes section from AST and removes corresponding bytes from buffer
{
  const ast = createEmptyModuleAst();
  const { uint8Buffer: buf1 } = createEmptySection(ast, wasmHeader, "type");
  const { uint8Buffer: buf2 } = createEmptySection(ast, buf1, "import");
  assert.equal(ast.body[0].metadata.sections.length, 2);

  const bufAfterRemove = deleteSection(ast, buf2, "type");
  assert.equal(ast.body[0].metadata.sections.length, 1);
  assert.equal(ast.body[0].metadata.sections[0].section, "import");
  assert.deepEqual(
    Buffer.from(bufAfterRemove),
    Buffer.from([0x00, 0x61, 0x73, 0x6d, 0x01, 0x00, 0x00, 0x00, 0x02, 0x01, 0x00])
  );

  const bufEmpty = removeSections(ast, bufAfterRemove, "import");
  assert.equal(ast.body[0].metadata.sections.length, 0);
  assert.deepEqual(Buffer.from(bufEmpty), wasmHeader);
}

// Contract Assertion 5: removeSections and resize functions throw an Error when section does not exist in AST
{
  const ast = createEmptyModuleAst();
  const buf = Buffer.from(wasmHeader);

  assert.throws(() => {
    deleteSection(ast, buf, "nonexistent");
  }, /Section metadata not found/);

  assert.throws(() => {
    removeSections(ast, buf, "custom");
  }, /Section metadata not found/);

  assert.throws(() => {
    adjustSectionByteSize(ast, buf, "nonexistent", 1);
  }, /Section metadata not found/);

  assert.throws(() => {
    resizeSectionByteSize(ast, buf, "custom", 1);
  }, /Section metadata not found/);

  assert.throws(() => {
    adjustSectionVecSize(ast, buf, "nonexistent", 1);
  }, /Section metadata not found/);

  assert.throws(() => {
    resizeSectionVecSize(ast, buf, "custom", 1);
  }, /Section metadata not found/);
}

console.log("All contract tests passed successfully.");