Enable brotli decompression if it is available (#620)

* Enable brotli decompression if it is available

* Apply PR feedback

vcr/filters.py

@@ -6,6 +6,49 @@ from urllib.parse import urlencode, urlparse, urlunparse
 
 from .util import CaseInsensitiveDict
 
+try:
+    # This supports both brotli & brotlipy packages
+    import brotli
+except ImportError:
+    try:
+        import brotlicffi as brotli
+    except ImportError:
+        brotli = None
+
+
+def decompress_deflate(body):
+    try:
+        return zlib.decompress(body)
+    except zlib.error:
+        # Assume the response was already decompressed
+        return body
+
+
+def decompress_gzip(body):
+    # To (de-)compress gzip format, use wbits = zlib.MAX_WBITS | 16.
+    try:
+        return zlib.decompress(body, zlib.MAX_WBITS | 16)
+    except zlib.error:
+        # Assume the response was already decompressed
+        return body
+
+
+AVAILABLE_DECOMPRESSORS = {
+    "deflate": decompress_deflate,
+    "gzip": decompress_gzip,
+}
+
+if brotli is not None:
+
+    def decompress_brotli(body):
+        try:
+            return brotli.decompress(body)
+        except brotli.error:
+            # Assume the response was already decompressed
+            return body
+
+    AVAILABLE_DECOMPRESSORS["br"] = decompress_brotli
+
 
 def replace_headers(request, replacements):
     """Replace headers in request according to replacements.
@@ -136,45 +179,30 @@ def remove_post_data_parameters(request, post_data_parameters_to_remove):
 
 def decode_response(response):
     """
-    If the response is compressed with gzip or deflate:
+    If the response is compressed with any supported compression (gzip,
+    deflate, br if available):
       1. decompress the response body
       2. delete the content-encoding header
       3. update content-length header to decompressed length
     """
 
-    def is_compressed(headers):
-        encoding = headers.get("content-encoding", [])
-        return encoding and encoding[0] in ("gzip", "deflate")
-
-    def decompress_body(body, encoding):
-        """Returns decompressed body according to encoding using zlib.
-        to (de-)compress gzip format, use wbits = zlib.MAX_WBITS | 16
-        """
-        if not body:
-            return ""
-        if encoding == "gzip":
-            try:
-                return zlib.decompress(body, zlib.MAX_WBITS | 16)
-            except zlib.error:
-                return body  # assumes that the data was already decompressed
-        else:  # encoding == 'deflate'
-            try:
-                return zlib.decompress(body)
-            except zlib.error:
-                return body  # assumes that the data was already decompressed
-
     # Deepcopy here in case `headers` contain objects that could
     # be mutated by a shallow copy and corrupt the real response.
     response = copy.deepcopy(response)
     headers = CaseInsensitiveDict(response["headers"])
-    if is_compressed(headers):
-        encoding = headers["content-encoding"][0]
-        headers["content-encoding"].remove(encoding)
-        if not headers["content-encoding"]:
-            del headers["content-encoding"]
+    content_encoding = headers.get("content-encoding")
+    if not content_encoding:
+        return response
+    decompressor = AVAILABLE_DECOMPRESSORS.get(content_encoding[0])
+    if not decompressor:
+        return response
 
-        new_body = decompress_body(response["body"]["string"], encoding)
-        response["body"]["string"] = new_body
-        headers["content-length"] = [str(len(new_body))]
-        response["headers"] = dict(headers)
+    headers["content-encoding"].remove(content_encoding[0])
+    if not headers["content-encoding"]:
+        del headers["content-encoding"]
+
+    new_body = decompressor(response["body"]["string"])
+    response["body"]["string"] = new_body
+    headers["content-length"] = [str(len(new_body))]
+    response["headers"] = dict(headers)
     return response