File size: 5,411 Bytes
26e6f31 | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 | from __future__ import annotations
import warnings
from collections import defaultdict
from typing import TYPE_CHECKING, Any
if TYPE_CHECKING:
from aws_lambda_powertools.shared.cookies import Cookie
class BaseHeadersSerializer:
"""
Helper class to correctly serialize headers and cookies for Amazon API Gateway,
ALB and Lambda Function URL response payload.
"""
def serialize(self, headers: dict[str, str | list[str]], cookies: list[Cookie]) -> dict[str, Any]:
"""
Serializes headers and cookies according to the request type.
Returns a dict that can be merged with the response payload.
Parameters
----------
headers: dict[str, str | list[str]]
A dictionary of headers to set in the response
cookies: list[Cookie]
A list of cookies to set in the response
"""
raise NotImplementedError()
class HttpApiHeadersSerializer(BaseHeadersSerializer):
def serialize(self, headers: dict[str, str | list[str]], cookies: list[Cookie]) -> dict[str, Any]:
"""
When using HTTP APIs or LambdaFunctionURLs, everything is taken care automatically for us.
We can directly assign a list of cookies and a dict of headers to the response payload, and the
runtime will automatically serialize them correctly on the output.
https://docs.aws.amazon.com/apigateway/latest/developerguide/http-api-develop-integrations-lambda.html#http-api-develop-integrations-lambda.proxy-format
https://docs.aws.amazon.com/apigateway/latest/developerguide/http-api-develop-integrations-lambda.html#http-api-develop-integrations-lambda.response
"""
# Format 2.0 doesn't have multiValueHeaders or multiValueQueryStringParameters fields.
# Duplicate headers are combined with commas and included in the headers field.
combined_headers: dict[str, str] = {}
for key, values in headers.items():
# omit headers with explicit null values
if values is None:
continue
if isinstance(values, str):
combined_headers[key] = values
else:
combined_headers[key] = ", ".join(values)
return {"headers": combined_headers, "cookies": list(map(str, cookies))}
class MultiValueHeadersSerializer(BaseHeadersSerializer):
def serialize(self, headers: dict[str, str | list[str]], cookies: list[Cookie]) -> dict[str, Any]:
"""
When using REST APIs, headers can be encoded using the `multiValueHeaders` key on the response.
This is also the case when using an ALB integration with the `multiValueHeaders` option enabled.
The solution covers headers with just one key or multiple keys.
https://docs.aws.amazon.com/apigateway/latest/developerguide/set-up-lambda-proxy-integrations.html#api-gateway-simple-proxy-for-lambda-output-format
https://docs.aws.amazon.com/elasticloadbalancing/latest/application/lambda-functions.html#multi-value-headers-response
"""
payload: dict[str, list[str]] = defaultdict(list)
for key, values in headers.items():
# omit headers with explicit null values
if values is None:
continue
if isinstance(values, str):
payload[key].append(values)
else:
payload[key].extend(values)
if cookies:
payload.setdefault("Set-Cookie", [])
for cookie in cookies:
payload["Set-Cookie"].append(str(cookie))
return {"multiValueHeaders": payload}
class SingleValueHeadersSerializer(BaseHeadersSerializer):
def serialize(self, headers: dict[str, str | list[str]], cookies: list[Cookie]) -> dict[str, Any]:
"""
The ALB integration has `multiValueHeaders` disabled by default.
If we try to set multiple headers with the same key, or more than one cookie, print a warning.
https://docs.aws.amazon.com/elasticloadbalancing/latest/application/lambda-functions.html#respond-to-load-balancer
"""
payload: dict[str, dict[str, str]] = {}
payload.setdefault("headers", {})
if cookies:
if len(cookies) > 1:
warnings.warn(
"Can't encode more than one cookie in the response. Sending the last cookie only. "
"Did you enable multiValueHeaders on the ALB Target Group?",
stacklevel=2,
)
# We can only send one cookie, send the last one
payload["headers"]["Set-Cookie"] = str(cookies[-1])
for key, values in headers.items():
# omit headers with explicit null values
if values is None:
continue
if isinstance(values, str):
payload["headers"][key] = values
else:
if len(values) > 1:
warnings.warn(
f"Can't encode more than one header value for the same key ('{key}') in the response. "
"Did you enable multiValueHeaders on the ALB Target Group?",
stacklevel=2,
)
# We can only set one header per key, send the last one
payload["headers"][key] = values[-1]
return payload
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