Move flask_compress dependency to extras require

CHANGELOG.md

@@ -26,6 +26,10 @@ This project adheres to [Semantic Versioning](https://semver.org/).
 - [#2265](https://github.com/plotly/dash/pull/2265) Removed deprecated `before_first_request` as reported in [#2177](https://github.com/plotly/dash/issues/2177).
 - [#2257](https://github.com/plotly/dash/pull/2257) Fix tuple types in the TypeScript component generator.
 
+### Changed
+
+- [#2291](https://github.com/plotly/dash/pull/2291) Move `flask-compress` dependency to new extras requires `dash[compress]`
+
 ## [2.6.2] - 2022-09-23
 
 ### Fixed

dash/dash.py

@@ -18,7 +18,6 @@
 from textwrap import dedent
 
 import flask
-from flask_compress import Compress
 
 from pkg_resources import get_distribution, parse_version
 
@@ -69,9 +68,6 @@
     _parse_query_string,
 )
 
-
-_flask_compress_version = parse_version(get_distribution("flask-compress").version)
-
 # Add explicit mapping for map files
 mimetypes.add_type("application/json", ".map", True)
 
@@ -261,6 +257,7 @@ class Dash:
     :type serve_locally: boolean
 
     :param compress: Use gzip to compress files and data served by Flask.
+        To use this option, you need to install dash[compress]
         Default ``False``
     :type compress: boolean
 
@@ -379,16 +376,6 @@ def __init__(  # pylint: disable=too-many-statements
         else:
             raise ValueError("server must be a Flask app or a boolean")
 
-        if (
-            self.server is not None
-            and not hasattr(self.server.config, "COMPRESS_ALGORITHM")
-            and _flask_compress_version >= parse_version("1.6.0")
-        ):
-            # flask-compress==1.6.0 changed default to ['br', 'gzip']
-            # and non-overridable default compression with Brotli is
-            # causing performance issues
-            self.server.config["COMPRESS_ALGORITHM"] = ["gzip"]
-
         base_prefix, routes_prefix, requests_prefix = pathname_configs(
             url_base_pathname, routes_pathname_prefix, requests_pathname_prefix
         )
@@ -540,8 +527,28 @@ def init_app(self, app=None, **kwargs):
         )
 
         if config.compress:
-            # gzip
-            Compress(self.server)
+            try:
+                # pylint: disable=import-outside-toplevel
+                from flask_compress import Compress
+
+                # gzip
+                Compress(self.server)
+
+                _flask_compress_version = parse_version(
+                    get_distribution("flask-compress").version
+                )
+
+                if not hasattr(
+                    self.server.config, "COMPRESS_ALGORITHM"
+                ) and _flask_compress_version >= parse_version("1.6.0"):
+                    # flask-compress==1.6.0 changed default to ['br', 'gzip']
+                    # and non-overridable default compression with Brotli is
+                    # causing performance issues
+                    self.server.config["COMPRESS_ALGORITHM"] = ["gzip"]
+            except ImportError as error:
+                raise ImportError(
+                    "To use the compress option, you need to install dash[compress]"
+                ) from error
 
         @self.server.errorhandler(PreventUpdate)
         def _handle_error(_):

requires-compress.txt

@@ -0,0 +1 @@
+flask-compress

requires-install.txt

@@ -1,5 +1,4 @@
 Flask>=1.0.4
-flask-compress
 plotly>=5.0.0
 dash_html_components==2.0.0
 dash_core_components==2.0.0

setup.py

@@ -33,6 +33,7 @@ def read_req_file(req_type):
         "testing": read_req_file("testing"),
         "celery": read_req_file("celery"),
         "diskcache": read_req_file("diskcache"),
+        "compress": read_req_file("compress"),
     },
     entry_points={
         "console_scripts": [

tests/unit/test_configs.py

@@ -482,3 +482,8 @@ def test_debug_mode_enable_dev_tools(empty_environ, debug_env, debug, expected):
     app = Dash()
     app.enable_dev_tools(debug=debug)
     assert app._dev_tools.ui == expected
+
+
+def test_missing_flask_compress_raises():
+    with pytest.raises(ImportError):
+        Dash(compress=True)