test.py

"""Simplest example to show json.load()/LimitedStream issue.

Steps to reproduce:

 * $ FLASK_APP=test.py flask run
 * $ echo '{"test": "data"}' | curl -X PUT -d @- -H Content-Type:application/json http://localhost:5000/get_json # works
 * $ echo '{"test": "data"}' | curl -X PUT -d @- -H Content-Type:application/json http://localhost:5000/ # errors out:

Traceback:
  [...]
  File "[...]/venv/lib/python3.5/site-packages/flask/json.py", line 37, in _wrap_reader_for_text
    fp = io.TextIOWrapper(io.BufferedReader(fp), encoding)
AttributeError: 'LimitedStream' object has no attribute 'readable'

request.get_json() doesn't use json.load; instead uses json.loads() with the
fetched request data as a string.

request.stream wraps the raw input (request.input_stream/
request.environ['wsgi.input']) with LimitedStream to avoid hanging at the end
of the file. However LimitedStream doesn't implement everything required for
io.BufferedReader, which is an intermediate step in json.load()
"""

from flask import Flask, request
from flask import json
app = Flask(__name__)

@app.route("/", methods=['GET', 'PUT'])
def errors():
    if request.method == 'PUT':
        data = json.load(request.stream)
        print('data received:', data)
        return 'OK\n'


@app.route("/get_json", methods=['GET', 'PUT'])
def works():
    if request.method == 'PUT':
        data = request.get_json()
        print('json received:', data)
        return 'OK\n'