feat: Decompression Interceptor (#4317)

Co-authored-by: Carlos Fuentes <[email protected]>
Co-authored-by: Aras Abbasi <[email protected]>

Author: 3 people

docs/docs/api/Dispatcher.md

@@ -1094,6 +1094,65 @@ await client.request({
 });
 ```
 
+##### `decompress`
+
+⚠️ The decompress interceptor is experimental and subject to change.
+
+The `decompress` interceptor automatically decompresses response bodies that are compressed with gzip, deflate, brotli, or zstd compression. It removes the `content-encoding` and `content-length` headers from decompressed responses and supports RFC-9110 compliant multiple encodings.
+
+**Options**
+
+- `skipErrorResponses` - Whether to skip decompression for error responses (status codes >= 400). Default: `true`.
+- `skipStatusCodes` - Array of status codes to skip decompression for. Default: `[204, 304]`.
+
+**Example - Basic Decompress Interceptor**
+
+```js
+const { Client, interceptors } = require("undici");
+const { decompress } = interceptors;
+
+const client = new Client("http://example.com").compose(
+  decompress()
+);
+
+// Automatically decompresses gzip/deflate/brotli/zstd responses
+const response = await client.request({
+  method: "GET",
+  path: "/"
+});
+```
+
+**Example - Custom Options**
+
+```js
+const { Client, interceptors } = require("undici");
+const { decompress } = interceptors;
+
+const client = new Client("http://example.com").compose(
+  decompress({
+    skipErrorResponses: false, // Decompress 5xx responses
+    skipStatusCodes: [204, 304, 201] // Skip these status codes
+  })
+);
+```
+
+**Supported Encodings**
+
+- `gzip` / `x-gzip` - GZIP compression
+- `deflate` / `x-compress` - DEFLATE compression  
+- `br` - Brotli compression
+- `zstd` - Zstandard compression
+- Multiple encodings (e.g., `gzip, deflate`) are supported per RFC-9110
+
+**Behavior**
+
+- Skips decompression for status codes < 200 or >= 400 (configurable)
+- Skips decompression for 204 No Content and 304 Not Modified by default
+- Removes `content-encoding` and `content-length` headers when decompressing
+- Passes through unsupported encodings unchanged
+- Handles case-insensitive encoding names
+- Supports streaming decompression without buffering
+
 ##### `Cache Interceptor`
 
 The `cache` interceptor implements client-side response caching as described in

index.js

@@ -46,7 +46,8 @@ module.exports.interceptors = {
   retry: require('./lib/interceptor/retry'),
   dump: require('./lib/interceptor/dump'),
   dns: require('./lib/interceptor/dns'),
-  cache: require('./lib/interceptor/cache')
+  cache: require('./lib/interceptor/cache'),
+  decompress: require('./lib/interceptor/decompress')
 }
 
 module.exports.cacheStores = {

lib/interceptor/decompress.js

@@ -0,0 +1,253 @@
+'use strict'
+
+const { createInflate, createGunzip, createBrotliDecompress, createZstdDecompress } = require('node:zlib')
+const { pipeline } = require('node:stream')
+const DecoratorHandler = require('../handler/decorator-handler')
+
+/** @typedef {import('node:stream').Transform} Transform */
+/** @typedef {import('node:stream').Transform} Controller */
+/** @typedef {Transform&import('node:zlib').Zlib} DecompressorStream */
+
+/** @type {Record<string, () => DecompressorStream>} */
+const supportedEncodings = {
+  gzip: createGunzip,
+  'x-gzip': createGunzip,
+  br: createBrotliDecompress,
+  deflate: createInflate,
+  compress: createInflate,
+  'x-compress': createInflate,
+  ...(createZstdDecompress ? { zstd: createZstdDecompress } : {})
+}
+
+const defaultSkipStatusCodes = /** @type {const} */ ([204, 304])
+
+let warningEmitted = /** @type {boolean} */ (false)
+
+/**
+ * @typedef {Object} DecompressHandlerOptions
+ * @property {number[]|Readonly<number[]>} [skipStatusCodes=[204, 304]] - List of status codes to skip decompression for
+ * @property {boolean} [skipErrorResponses] - Whether to skip decompression for error responses (status codes >= 400)
+ */
+
+class DecompressHandler extends DecoratorHandler {
+  /** @type {Transform[]} */
+  #decompressors = []
+  /** @type {NodeJS.WritableStream&NodeJS.ReadableStream|null} */
+  #pipelineStream
+  /** @type {Readonly<number[]>} */
+  #skipStatusCodes
+  /** @type {boolean} */
+  #skipErrorResponses
+
+  constructor (handler, { skipStatusCodes = defaultSkipStatusCodes, skipErrorResponses = true } = {}) {
+    super(handler)
+    this.#skipStatusCodes = skipStatusCodes
+    this.#skipErrorResponses = skipErrorResponses
+  }
+
+  /**
+   * Determines if decompression should be skipped based on encoding and status code
+   * @param {string} contentEncoding - Content-Encoding header value
+   * @param {number} statusCode - HTTP status code of the response
+   * @returns {boolean} - True if decompression should be skipped
+   */
+  #shouldSkipDecompression (contentEncoding, statusCode) {
+    if (!contentEncoding || statusCode < 200) return true
+    if (this.#skipStatusCodes.includes(statusCode)) return true
+    if (this.#skipErrorResponses && statusCode >= 400) return true
+    return false
+  }
+
+  /**
+   * Creates a chain of decompressors for multiple content encodings
+   *
+   * @param {string} encodings - Comma-separated list of content encodings
+   * @returns {Array<DecompressorStream>} - Array of decompressor streams
+   */
+  #createDecompressionChain (encodings) {
+    const parts = encodings.split(',')
+
+    /** @type {DecompressorStream[]} */
+    const decompressors = []
+
+    for (let i = parts.length - 1; i >= 0; i--) {
+      const encoding = parts[i].trim()
+      if (!encoding) continue
+
+      if (!supportedEncodings[encoding]) {
+        decompressors.length = 0 // Clear if unsupported encoding
+        return decompressors // Unsupported encoding
+      }
+
+      decompressors.push(supportedEncodings[encoding]())
+    }
+
+    return decompressors
+  }
+
+  /**
+   * Sets up event handlers for a decompressor stream using readable events
+   * @param {DecompressorStream} decompressor - The decompressor stream
+   * @param {Controller} controller - The controller to coordinate with
+   * @returns {void}
+   */
+  #setupDecompressorEvents (decompressor, controller) {
+    decompressor.on('readable', () => {
+      let chunk
+      while ((chunk = decompressor.read()) !== null) {
+        const result = super.onResponseData(controller, chunk)
+        if (result === false) {
+          break
+        }
+      }
+    })
+
+    decompressor.on('error', (error) => {
+      super.onResponseError(controller, error)
+    })
+  }
+
+  /**
+   * Sets up event handling for a single decompressor
+   * @param {Controller} controller - The controller to handle events
+   * @returns {void}
+   */
+  #setupSingleDecompressor (controller) {
+    const decompressor = this.#decompressors[0]
+    this.#setupDecompressorEvents(decompressor, controller)
+
+    decompressor.on('end', () => {
+      super.onResponseEnd(controller, {})
+    })
+  }
+
+  /**
+   * Sets up event handling for multiple chained decompressors using pipeline
+   * @param {Controller} controller - The controller to handle events
+   * @returns {void}
+   */
+  #setupMultipleDecompressors (controller) {
+    const lastDecompressor = this.#decompressors[this.#decompressors.length - 1]
+    this.#setupDecompressorEvents(lastDecompressor, controller)
+
+    this.#pipelineStream = pipeline(this.#decompressors, (err) => {
+      if (err) {
+        super.onResponseError(controller, err)
+        return
+      }
+      super.onResponseEnd(controller, {})
+    })
+  }
+
+  /**
+   * Cleans up decompressor references to prevent memory leaks
+   * @returns {void}
+   */
+  #cleanupDecompressors () {
+    this.#decompressors.length = 0
+    this.#pipelineStream = null
+  }
+
+  /**
+   * @param {Controller} controller
+   * @param {number} statusCode
+   * @param {Record<string, string | string[] | undefined>} headers
+   * @param {string} statusMessage
+   * @returns {void}
+   */
+  onResponseStart (controller, statusCode, headers, statusMessage) {
+    const contentEncoding = headers['content-encoding']
+
+    // If content encoding is not supported or status code is in skip list
+    if (this.#shouldSkipDecompression(contentEncoding, statusCode)) {
+      return super.onResponseStart(controller, statusCode, headers, statusMessage)
+    }
+
+    const decompressors = this.#createDecompressionChain(contentEncoding.toLowerCase())
+
+    if (decompressors.length === 0) {
+      this.#cleanupDecompressors()
+      return super.onResponseStart(controller, statusCode, headers, statusMessage)
+    }
+
+    this.#decompressors = decompressors
+
+    // Remove compression headers since we're decompressing
+    const { 'content-encoding': _, 'content-length': __, ...newHeaders } = headers
+
+    if (this.#decompressors.length === 1) {
+      this.#setupSingleDecompressor(controller)
+    } else {
+      this.#setupMultipleDecompressors(controller)
+    }
+
+    super.onResponseStart(controller, statusCode, newHeaders, statusMessage)
+  }
+
+  /**
+   * @param {Controller} controller
+   * @param {Buffer} chunk
+   * @returns {void}
+   */
+  onResponseData (controller, chunk) {
+    if (this.#decompressors.length > 0) {
+      this.#decompressors[0].write(chunk)
+      return
+    }
+    super.onResponseData(controller, chunk)
+  }
+
+  /**
+   * @param {Controller} controller
+   * @param {Record<string, string | string[]> | undefined} trailers
+   * @returns {void}
+   */
+  onResponseEnd (controller, trailers) {
+    if (this.#decompressors.length > 0) {
+      this.#decompressors[0].end()
+      this.#cleanupDecompressors()
+      return
+    }
+    super.onResponseEnd(controller, trailers)
+  }
+
+  /**
+   * @param {Controller} controller
+   * @param {Error} err
+   * @returns {void}
+   */
+  onResponseError (controller, err) {
+    if (this.#decompressors.length > 0) {
+      for (const decompressor of this.#decompressors) {
+        decompressor.destroy(err)
+      }
+      this.#cleanupDecompressors()
+    }
+    super.onResponseError(controller, err)
+  }
+}
+
+/**
+ * Creates a decompression interceptor for HTTP responses
+ * @param {DecompressHandlerOptions} [options] - Options for the interceptor
+ * @returns {Function} - Interceptor function
+ */
+function createDecompressInterceptor (options = {}) {
+  // Emit experimental warning only once
+  if (!warningEmitted) {
+    process.emitWarning(
+      'DecompressInterceptor is experimental and subject to change',
+      'ExperimentalWarning'
+    )
+    warningEmitted = true
+  }
+
+  return (dispatch) => {
+    return (opts, handler) => {
+      const decompressHandler = new DecompressHandler(handler, options)
+      return dispatch(opts, decompressHandler)
+    }
+  }
+}
+
+module.exports = createDecompressInterceptor