Make charset auto-detection optional. (#2165)

* Add Response(..., default_encoding=...)

* Add tests for Response(..., default_encoding=...)

* Add Client(..., default_encoding=...)

* Switch default encoding to 'utf-8' instead of 'autodetect'

* Make charset_normalizer an optional dependancy, not a mandatory one.

* Documentation

* Use callable for default_encoding

* Update tests for new charset autodetection API

* Update docs for new charset autodetection API

* Update requirements

* Drop charset_normalizer from requirements
This commit is contained in:
Tom Christie 2022-05-23 16:27:32 +01:00 committed by GitHub
parent 940d61b239
commit 1c33a2854e
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11 changed files with 245 additions and 54 deletions

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@ -128,7 +128,6 @@ The HTTPX project relies on these excellent libraries:
* `httpcore` - The underlying transport implementation for `httpx`.
* `h11` - HTTP/1.1 support.
* `certifi` - SSL certificates.
* `charset_normalizer` - Charset auto-detection.
* `rfc3986` - URL parsing & normalization.
* `idna` - Internationalized domain name support.
* `sniffio` - Async library autodetection.

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@ -129,7 +129,6 @@ HTTPX项目依赖于这些优秀的库:
* `h11` - HTTP/1.1 support.
* `h2` - HTTP/2 support. *(Optional, with `httpx[http2]`)*
* `certifi` - SSL certificates.
* `charset_normalizer` - Charset auto-detection.
* `rfc3986` - URL parsing & normalization.
* `idna` - Internationalized domain name support.
* `sniffio` - Async library autodetection.

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@ -145,6 +145,88 @@ URL('http://httpbin.org/headers')
For a list of all available client parameters, see the [`Client`](api.md#client) API reference.
---
## Character set encodings and auto-detection
When accessing `response.text`, we need to decode the response bytes into a unicode text representation.
By default `httpx` will use `"charset"` information included in the response `Content-Type` header to determine how the response bytes should be decoded into text.
In cases where no charset information is included on the response, the default behaviour is to assume "utf-8" encoding, which is by far the most widely used text encoding on the internet.
### Using the default encoding
To understand this better let's start by looking at the default behaviour for text decoding...
```python
import httpx
# Instantiate a client with the default configuration.
client = httpx.Client()
# Using the client...
response = client.get(...)
print(response.encoding) # This will either print the charset given in
# the Content-Type charset, or else "utf-8".
print(response.text) # The text will either be decoded with the Content-Type
# charset, or using "utf-8".
```
This is normally absolutely fine. Most servers will respond with a properly formatted Content-Type header, including a charset encoding. And in most cases where no charset encoding is included, UTF-8 is very likely to be used, since it is so widely adopted.
### Using an explicit encoding
In some cases we might be making requests to a site where no character set information is being set explicitly by the server, but we know what the encoding is. In this case it's best to set the default encoding explicitly on the client.
```python
import httpx
# Instantiate a client with a Japanese character set as the default encoding.
client = httpx.Client(default_encoding="shift-jis")
# Using the client...
response = client.get(...)
print(response.encoding) # This will either print the charset given in
# the Content-Type charset, or else "shift-jis".
print(response.text) # The text will either be decoded with the Content-Type
# charset, or using "shift-jis".
```
### Using character set auto-detection
In cases where the server is not reliably including character set information, and where we don't know what encoding is being used, we can enable auto-detection to make a best-guess attempt when decoding from bytes to text.
To use auto-detection you need to set the `default_encoding` argument to a callable instead of a string. This callable should be a function which takes the input bytes as an argument and returns the character set to use for decoding those bytes to text.
There are two widely used Python packages which both handle this functionality:
* [`chardet`](https://chardet.readthedocs.io/) - This is a well established package, and is a port of [the auto-detection code in Mozilla](https://www-archive.mozilla.org/projects/intl/chardet.html).
* [`charset-normalizer`](https://charset-normalizer.readthedocs.io/) - A newer package, motivated by `chardet`, with a different approach.
Let's take a look at installing autodetection using one of these packages...
```shell
$ pip install httpx
$ pip install chardet
```
Once `chardet` is installed, we can configure a client to use character-set autodetection.
```python
import httpx
import chardet
def autodetect(content):
return chardet.detect(content).get("encoding")
# Using a client with character-set autodetection enabled.
client = httpx.Client(default_encoding=autodetect)
response = client.get(...)
print(response.encoding) # This will either print the charset given in
# the Content-Type charset, or else the auto-detected
# character set.
print(response.text)
```
---
## Calling into Python Web Apps
You can configure an `httpx` client to call directly into a Python web application using the WSGI protocol.

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@ -109,7 +109,6 @@ The HTTPX project relies on these excellent libraries:
* `httpcore` - The underlying transport implementation for `httpx`.
* `h11` - HTTP/1.1 support.
* `certifi` - SSL certificates.
* `charset_normalizer` - Charset auto-detection.
* `rfc3986` - URL parsing & normalization.
* `idna` - Internationalized domain name support.
* `sniffio` - Async library autodetection.

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@ -168,6 +168,7 @@ class BaseClient:
] = None,
base_url: URLTypes = "",
trust_env: bool = True,
default_encoding: typing.Union[str, typing.Callable[[bytes], str]] = "utf-8",
):
event_hooks = {} if event_hooks is None else event_hooks
@ -185,6 +186,7 @@ class BaseClient:
"response": list(event_hooks.get("response", [])),
}
self._trust_env = trust_env
self._default_encoding = default_encoding
self._netrc = NetRCInfo()
self._state = ClientState.UNOPENED
@ -611,6 +613,9 @@ class Client(BaseClient):
rather than sending actual network requests.
* **trust_env** - *(optional)* Enables or disables usage of environment
variables for configuration.
* **default_encoding** - *(optional)* The default encoding to use for decoding
response text, if no charset information is included in a response Content-Type
header. Set to a callable for automatic character set detection. Default: "utf-8".
"""
def __init__(
@ -637,6 +642,7 @@ class Client(BaseClient):
transport: typing.Optional[BaseTransport] = None,
app: typing.Optional[typing.Callable] = None,
trust_env: bool = True,
default_encoding: typing.Union[str, typing.Callable[[bytes], str]] = "utf-8",
):
super().__init__(
auth=auth,
@ -649,6 +655,7 @@ class Client(BaseClient):
event_hooks=event_hooks,
base_url=base_url,
trust_env=trust_env,
default_encoding=default_encoding,
)
if http2:
@ -1002,6 +1009,7 @@ class Client(BaseClient):
response.stream, response=response, timer=timer
)
self.cookies.extract_cookies(response)
response.default_encoding = self._default_encoding
status = f"{response.status_code} {response.reason_phrase}"
response_line = f"{response.http_version} {status}"
@ -1326,6 +1334,9 @@ class AsyncClient(BaseClient):
rather than sending actual network requests.
* **trust_env** - *(optional)* Enables or disables usage of environment
variables for configuration.
* **default_encoding** - *(optional)* The default encoding to use for decoding
response text, if no charset information is included in a response Content-Type
header. Set to a callable for automatic character set detection. Default: "utf-8".
"""
def __init__(
@ -1352,6 +1363,7 @@ class AsyncClient(BaseClient):
transport: typing.Optional[AsyncBaseTransport] = None,
app: typing.Optional[typing.Callable] = None,
trust_env: bool = True,
default_encoding: str = "utf-8",
):
super().__init__(
auth=auth,
@ -1364,6 +1376,7 @@ class AsyncClient(BaseClient):
event_hooks=event_hooks,
base_url=base_url,
trust_env=trust_env,
default_encoding=default_encoding,
)
if http2:
@ -1708,6 +1721,7 @@ class AsyncClient(BaseClient):
response.stream, response=response, timer=timer
)
self.cookies.extract_cookies(response)
response.default_encoding = self._default_encoding
status = f"{response.status_code} {response.reason_phrase}"
response_line = f"{response.http_version} {status}"

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@ -7,8 +7,6 @@ import urllib.request
from collections.abc import MutableMapping
from http.cookiejar import Cookie, CookieJar
import charset_normalizer
from ._content import ByteStream, UnattachedStream, encode_request, encode_response
from ._decoders import (
SUPPORTED_DECODERS,
@ -445,6 +443,7 @@ class Response:
request: typing.Optional[Request] = None,
extensions: typing.Optional[dict] = None,
history: typing.Optional[typing.List["Response"]] = None,
default_encoding: typing.Union[str, typing.Callable[[bytes], str]] = "utf-8",
):
self.status_code = status_code
self.headers = Headers(headers)
@ -461,6 +460,8 @@ class Response:
self.is_closed = False
self.is_stream_consumed = False
self.default_encoding = default_encoding
if stream is None:
headers, stream = encode_response(content, text, html, json)
self._prepare(headers)
@ -569,14 +570,18 @@ class Response:
* `.encoding = <>` has been set explicitly.
* The encoding as specified by the charset parameter in the Content-Type header.
* The encoding as determined by `charset_normalizer`.
* UTF-8.
* The encoding as determined by `default_encoding`, which may either be
a string like "utf-8" indicating the encoding to use, or may be a callable
which enables charset autodetection.
"""
if not hasattr(self, "_encoding"):
encoding = self.charset_encoding
if encoding is None or not is_known_encoding(encoding):
encoding = self.apparent_encoding
self._encoding = encoding
if isinstance(self.default_encoding, str):
encoding = self.default_encoding
elif hasattr(self, "_content"):
encoding = self.default_encoding(self._content)
self._encoding = encoding or "utf-8"
return self._encoding
@encoding.setter
@ -598,19 +603,6 @@ class Response:
return params["charset"].strip("'\"")
@property
def apparent_encoding(self) -> typing.Optional[str]:
"""
Return the encoding, as determined by `charset_normalizer`.
"""
content = getattr(self, "_content", b"")
if len(content) < 32:
# charset_normalizer will issue warnings if we run it with
# fewer bytes than this cutoff.
return None
match = charset_normalizer.from_bytes(self.content).best()
return None if match is None else match.encoding
def _get_content_decoder(self) -> ContentDecoder:
"""
Returns a decoder instance which can be used to decode the raw byte

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@ -4,7 +4,10 @@
# Reference: https://github.com/encode/httpx/pull/1721#discussion_r661241588
-e .[brotli,cli,http2,socks]
charset-normalizer==2.0.6
# Optional charset auto-detection
# Used in our test cases
chardet==4.0.0
types-chardet==4.0.4
# Documentation
mkdocs==1.3.0

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@ -57,7 +57,6 @@ setup(
zip_safe=False,
install_requires=[
"certifi",
"charset_normalizer",
"sniffio",
"rfc3986[idna2008]>=1.3,<2",
"httpcore>=0.15.0,<0.16.0",

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@ -1,11 +1,16 @@
import typing
from datetime import timedelta
import chardet
import pytest
import httpx
def autodetect(content):
return chardet.detect(content).get("encoding")
def test_get(server):
url = server.url
with httpx.Client(http2=True) as http:
@ -15,7 +20,7 @@ def test_get(server):
assert response.content == b"Hello, world!"
assert response.text == "Hello, world!"
assert response.http_version == "HTTP/1.1"
assert response.encoding is None
assert response.encoding == "utf-8"
assert response.request.url == url
assert response.headers
assert response.is_redirect is False
@ -398,3 +403,58 @@ def test_server_extensions(server):
response = client.get(url)
assert response.status_code == 200
assert response.extensions["http_version"] == b"HTTP/1.1"
def test_client_decode_text_using_autodetect():
# Ensure that a 'default_encoding=autodetect' on the response allows for
# encoding autodetection to be used when no "Content-Type: text/plain; charset=..."
# info is present.
#
# Here we have some french text encoded with ISO-8859-1, rather than UTF-8.
text = (
"Non-seulement Despréaux ne se trompait pas, mais de tous les écrivains "
"que la France a produits, sans excepter Voltaire lui-même, imprégné de "
"l'esprit anglais par son séjour à Londres, c'est incontestablement "
"Molière ou Poquelin qui reproduit avec l'exactitude la plus vive et la "
"plus complète le fond du génie français."
)
def cp1252_but_no_content_type(request):
content = text.encode("ISO-8859-1")
return httpx.Response(200, content=content)
transport = httpx.MockTransport(cp1252_but_no_content_type)
with httpx.Client(transport=transport, default_encoding=autodetect) as client:
response = client.get("http://www.example.com")
assert response.status_code == 200
assert response.reason_phrase == "OK"
assert response.encoding == "ISO-8859-1"
assert response.text == text
def test_client_decode_text_using_explicit_encoding():
# Ensure that a 'default_encoding="..."' on the response is used for text decoding
# when no "Content-Type: text/plain; charset=..."" info is present.
#
# Here we have some french text encoded with ISO-8859-1, rather than UTF-8.
text = (
"Non-seulement Despréaux ne se trompait pas, mais de tous les écrivains "
"que la France a produits, sans excepter Voltaire lui-même, imprégné de "
"l'esprit anglais par son séjour à Londres, c'est incontestablement "
"Molière ou Poquelin qui reproduit avec l'exactitude la plus vive et la "
"plus complète le fond du génie français."
)
def cp1252_but_no_content_type(request):
content = text.encode("ISO-8859-1")
return httpx.Response(200, content=content)
transport = httpx.MockTransport(cp1252_but_no_content_type)
with httpx.Client(transport=transport, default_encoding=autodetect) as client:
response = client.get("http://www.example.com")
assert response.status_code == 200
assert response.reason_phrase == "OK"
assert response.encoding == "ISO-8859-1"
assert response.text == text

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@ -1,6 +1,7 @@
import json
import pickle
import chardet
import pytest
import httpx
@ -23,6 +24,10 @@ async def async_streaming_body():
yield b"world!"
def autodetect(content):
return chardet.detect(content).get("encoding")
def test_response():
response = httpx.Response(
200,
@ -164,9 +169,9 @@ def test_response_content_type_encoding():
assert response.encoding == "latin-1"
def test_response_autodetect_encoding():
def test_response_default_to_utf8_encoding():
"""
Autodetect encoding if there is no Content-Type header.
Default to utf-8 encoding if there is no Content-Type header.
"""
content = "おはようございます。".encode("utf-8")
response = httpx.Response(
@ -174,12 +179,12 @@ def test_response_autodetect_encoding():
content=content,
)
assert response.text == "おはようございます。"
assert response.encoding is None
assert response.encoding == "utf-8"
def test_response_fallback_to_autodetect():
def test_response_fallback_to_utf8_encoding():
"""
Fallback to autodetection if we get an invalid charset in the Content-Type header.
Fallback to utf-8 if we get an invalid charset in the Content-Type header.
"""
headers = {"Content-Type": "text-plain; charset=invalid-codec-name"}
content = "おはようございます。".encode("utf-8")
@ -189,7 +194,7 @@ def test_response_fallback_to_autodetect():
headers=headers,
)
assert response.text == "おはようございます。"
assert response.encoding is None
assert response.encoding == "utf-8"
def test_response_no_charset_with_ascii_content():
@ -205,7 +210,7 @@ def test_response_no_charset_with_ascii_content():
headers=headers,
)
assert response.status_code == 200
assert response.encoding is None
assert response.encoding == "utf-8"
assert response.text == "Hello, world!"
@ -222,46 +227,40 @@ def test_response_no_charset_with_utf8_content():
headers=headers,
)
assert response.text == "Unicode Snowman: ☃"
assert response.encoding is None
assert response.encoding == "utf-8"
def test_response_no_charset_with_iso_8859_1_content():
"""
A response with ISO 8859-1 encoded content should decode correctly,
even with no charset specified.
even with no charset specified, if autodetect is enabled.
"""
content = "Accented: Österreich abcdefghijklmnopqrstuzwxyz".encode("iso-8859-1")
headers = {"Content-Type": "text/plain"}
response = httpx.Response(
200,
content=content,
headers=headers,
200, content=content, headers=headers, default_encoding=autodetect
)
assert response.text == "Accented: Österreich abcdefghijklmnopqrstuzwxyz"
assert response.charset_encoding is None
assert response.apparent_encoding is not None
def test_response_no_charset_with_cp_1252_content():
"""
A response with Windows 1252 encoded content should decode correctly,
even with no charset specified.
even with no charset specified, if autodetect is enabled.
"""
content = "Euro Currency: € abcdefghijklmnopqrstuzwxyz".encode("cp1252")
headers = {"Content-Type": "text/plain"}
response = httpx.Response(
200,
content=content,
headers=headers,
200, content=content, headers=headers, default_encoding=autodetect
)
assert response.text == "Euro Currency: € abcdefghijklmnopqrstuzwxyz"
assert response.charset_encoding is None
assert response.apparent_encoding is not None
def test_response_non_text_encoding():
"""
Default to apparent encoding for non-text content-type headers.
Default to attempting utf-8 encoding for non-text content-type headers.
"""
headers = {"Content-Type": "image/png"}
response = httpx.Response(
@ -270,7 +269,7 @@ def test_response_non_text_encoding():
headers=headers,
)
assert response.text == "xyz"
assert response.encoding is None
assert response.encoding == "utf-8"
def test_response_set_explicit_encoding():
@ -307,7 +306,7 @@ def test_read():
assert response.status_code == 200
assert response.text == "Hello, world!"
assert response.encoding is None
assert response.encoding == "utf-8"
assert response.is_closed
content = response.read()
@ -322,7 +321,7 @@ def test_empty_read():
assert response.status_code == 200
assert response.text == ""
assert response.encoding is None
assert response.encoding == "utf-8"
assert response.is_closed
content = response.read()
@ -341,7 +340,7 @@ async def test_aread():
assert response.status_code == 200
assert response.text == "Hello, world!"
assert response.encoding is None
assert response.encoding == "utf-8"
assert response.is_closed
content = await response.aread()
@ -357,7 +356,7 @@ async def test_empty_aread():
assert response.status_code == 200
assert response.text == ""
assert response.encoding is None
assert response.encoding == "utf-8"
assert response.is_closed
content = await response.aread()
@ -968,3 +967,47 @@ async def test_response_async_streaming_picklable():
assert pickle_response.is_stream_consumed is True
assert pickle_response.content == b"Hello, world!"
assert pickle_response.num_bytes_downloaded == 13
def test_response_decode_text_using_autodetect():
# Ensure that a 'default_encoding="autodetect"' on the response allows for
# encoding autodetection to be used when no "Content-Type: text/plain; charset=..."
# info is present.
#
# Here we have some french text encoded with ISO-8859-1, rather than UTF-8.
text = (
"Non-seulement Despréaux ne se trompait pas, mais de tous les écrivains "
"que la France a produits, sans excepter Voltaire lui-même, imprégné de "
"l'esprit anglais par son séjour à Londres, c'est incontestablement "
"Molière ou Poquelin qui reproduit avec l'exactitude la plus vive et la "
"plus complète le fond du génie français."
)
content = text.encode("ISO-8859-1")
response = httpx.Response(200, content=content, default_encoding=autodetect)
assert response.status_code == 200
assert response.reason_phrase == "OK"
assert response.encoding == "ISO-8859-1"
assert response.text == text
def test_response_decode_text_using_explicit_encoding():
# Ensure that a 'default_encoding="..."' on the response is used for text decoding
# when no "Content-Type: text/plain; charset=..."" info is present.
#
# Here we have some french text encoded with Windows-1252, rather than UTF-8.
# https://en.wikipedia.org/wiki/Windows-1252
text = (
"Non-seulement Despréaux ne se trompait pas, mais de tous les écrivains "
"que la France a produits, sans excepter Voltaire lui-même, imprégné de "
"l'esprit anglais par son séjour à Londres, c'est incontestablement "
"Molière ou Poquelin qui reproduit avec l'exactitude la plus vive et la "
"plus complète le fond du génie français."
)
content = text.encode("cp1252")
response = httpx.Response(200, content=content, default_encoding="cp1252")
assert response.status_code == 200
assert response.reason_phrase == "OK"
assert response.encoding == "cp1252"
assert response.text == text

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@ -1,5 +1,6 @@
import zlib
import chardet
import pytest
import httpx
@ -184,17 +185,17 @@ def test_decoding_errors(header_value):
],
)
@pytest.mark.asyncio
async def test_text_decoder(data, encoding):
async def test_text_decoder_with_autodetect(data, encoding):
async def iterator():
nonlocal data
for chunk in data:
yield chunk
def autodetect(content):
return chardet.detect(content).get("encoding")
# Accessing `.text` on a read response.
response = httpx.Response(
200,
content=iterator(),
)
response = httpx.Response(200, content=iterator(), default_encoding=autodetect)
await response.aread()
assert response.text == (b"".join(data)).decode(encoding)