feat: add cloudformation loader (#16)

pyproject.toml

@@ -18,4 +18,5 @@ classifiers = [
 requires-python = ">=3.8"
 dependencies = [
     "fastapi == 0.104.1",
+    "PyYAML == 6.0.1",
 ]

src/cloudformation.py

@@ -0,0 +1,71 @@
+from pathlib import Path
+from typing import Any, Dict, List, Optional
+
+import yaml
+
+PREFIX = "Fn::"
+WITHOUT_PREFIX = ("Ref", "Condition")
+
+
+class CFTemplateNotFound(FileNotFoundError):
+    pass
+
+
+class CFBadTag(TypeError):
+    pass
+
+
+class CFBadNode(ValueError):
+    pass
+
+
+class CFLoader(yaml.SafeLoader):
+    pass
+
+
+def multi_constructor(loader: CFLoader, tag_suffix: str, node: yaml.nodes.Node) -> Dict[str, Any]:
+    tag = tag_suffix
+
+    if tag not in WITHOUT_PREFIX:
+        tag = f"{PREFIX}{tag}"
+
+    if tag == "Fn::GetAtt":
+        return {tag: construct_getatt(node)}
+    elif isinstance(node, yaml.ScalarNode):
+        return {tag: loader.construct_scalar(node)}
+    elif isinstance(node, yaml.SequenceNode):
+        return {tag: loader.construct_sequence(node)}
+    elif isinstance(node, yaml.MappingNode):
+        return {tag: loader.construct_mapping(node)}
+
+    raise CFBadTag(f"!{tag} <{type(node)}>")
+
+
+def construct_getatt(node: yaml.nodes.Node) -> List[Any]:
+    if isinstance(node.value, str):
+        return node.value.split(".", 1)
+    elif isinstance(node.value, list):
+        return [s.value for s in node.value]
+
+    raise CFBadNode(f"Type <{type(node.value)}>")
+
+
+CFLoader.add_multi_constructor("!", multi_constructor)
+
+
+def load(template: Optional[str] = None) -> Dict[str, Any]:
+    path: Optional[Path] = None
+
+    if isinstance(template, str):
+        path = Path(template)
+    else:
+        paths = (Path("template.yml"), Path("template.yaml"))
+        path_generator = (p for p in paths if p.is_file())
+        path = next(path_generator, None)
+
+    if path is None or not path.is_file():
+        filename = template or "[template.yml, template.yaml]"
+        raise CFTemplateNotFound(filename)
+
+    with path.open() as fp:
+        return yaml.load(fp, CFLoader)

tests/fixtures/templates/example1.yml

@@ -0,0 +1,37 @@
+AWSTemplateFormatVersion: '2010-09-09'
+Transform: AWS::Serverless-2016-10-31
+Description: >
+  sam-api
+
+  Sample SAM Template for sam-api
+
+Globals:
+  Function:
+    Timeout: 3
+
+Resources:
+  HelloWorldFunction:
+    Type: AWS::Serverless::Function
+    Properties:
+      CodeUri: hello_world/
+      Handler: app.lambda_handler
+      Runtime: python3.11
+      Architectures:
+        - x86_64
+      Events:
+        HelloWorld:
+          Type: Api
+          Properties:
+            Path: /hello
+            Method: get
+
+Outputs:
+  HelloWorldApi:
+    Description: "API Gateway endpoint URL for Prod stage for Hello World function"
+    Value: !Sub "https://${ServerlessRestApi}.execute-api.${AWS::Region}.amazonaws.com/Prod/hello/"
+  HelloWorldFunction:
+    Description: "Hello World Lambda Function ARN"
+    Value: !GetAtt HelloWorldFunction.Arn
+  HelloWorldFunctionIamRole:
+    Description: "Implicit IAM Role created for Hello World function"
+    Value: !GetAtt HelloWorldFunctionRole.Arn

tests/fixtures/templates/example2.yml

@@ -0,0 +1,77 @@
+AWSTemplateFormatVersion: "2010-09-09"
+Transform: AWS::Serverless-2016-10-31
+Description: >
+  sam-api
+
+  Sample SAM Template for sam-api
+
+Parameters:
+  Environment:
+    Type: String
+    Default: development
+
+Mappings:
+  Environments:
+    development:
+      LogLevel: DEBUG
+    staging:
+      LogLevel: WARNING
+    production:
+      LogLevel: ERROR
+
+Globals:
+  Function:
+    Runtime: python3.11
+    Timeout: 3
+    Environment:
+      Variables:
+        ENVIRONMENT:
+          Ref: Environment
+        LOG_LEVEL:
+          Fn::FindInMap:
+            - Environments
+            - Ref: Environment
+            - LogLevel
+
+Resources:
+  ApiGateway:
+    Type: AWS::Serverless::Api
+    Properties:
+      Name: sam-api
+      StageName: v1
+
+  ApiGatewayRole:
+    Type: AWS::IAM::Role
+    Properties:
+      AssumeRolePolicyDocument:
+        Version: "2012-10-17"
+        Statement:
+          - Effect: Allow
+            Principal:
+              Service:
+                - apigateway.amazonaws.com
+            Action:
+              - sts:AssumeRole
+
+  HelloWorldFunction:
+    Type: AWS::Serverless::Function
+    Properties:
+      CodeUri: hello_world/
+      Handler: app.lambda_handler
+      Events:
+        HelloWorld:
+          Type: Api
+          Properties:
+            Path: /hello
+            Method: get
+            RestApiId: !Ref ApiGateway
+
+Outputs:
+  HelloWorldApi:
+    Description: "API Gateway endpoint URL for Prod stage for Hello World function"
+    Value:
+      Fn::Sub: "https://${ApiGateway}.execute-api.${AWS::Region}.amazonaws.com/v1/hello/"
+  HelloWorldFunction:
+    Description: "Hello World Lambda Function ARN"
+    Value:
+      Fn::GetAtt: HelloWorldFunction.Arn

tests/fixtures/templates/example3.yml

@@ -0,0 +1,65 @@
+AWSTemplateFormatVersion: "2010-09-09"
+Transform: AWS::Serverless-2016-10-31
+Description: >
+  sam-api
+
+  Sample SAM Template for sam-api
+
+Parameters:
+  Environment:
+    Type: String
+    Default: development
+
+Mappings:
+  Environments:
+    development:
+      LogLevel: DEBUG
+    staging:
+      LogLevel: WARNING
+    production:
+      LogLevel: ERROR
+
+Globals:
+  Function:
+    Runtime: python3.11
+    Timeout: 3
+    Environment:
+      Variables:
+        ENVIRONMENT:
+          Ref: Environment
+        LOG_LEVEL:
+          Fn::FindInMap:
+            - Environments
+            - Ref: Environment
+            - LogLevel
+
+Resources:
+  ApiGateway:
+    Type: AWS::Serverless::Api
+    Properties:
+      Name: sam-api
+      StageName: v1
+      DefinitionBody:
+        Fn::Transform:
+          Name: AWS::Include
+          Parameters:
+            Location: "./swagger.yml"
+
+  ApiGatewayRole:
+    Type: AWS::IAM::Role
+    Properties:
+      AssumeRolePolicyDocument:
+        Version: "2012-10-17"
+        Statement:
+          - Effect: Allow
+            Principal:
+              Service:
+                - apigateway.amazonaws.com
+            Action:
+              - sts:AssumeRole
+
+  HelloWorldFunction:
+    Type: AWS::Serverless::Function
+    Properties:
+      CodeUri: hello_world/
+      Handler: app.lambda_handler

tests/fixtures/templates/swagger.yml

@@ -0,0 +1,80 @@
+openapi: "3.0.1"
+info:
+  title: "SAM API"
+  description: "Sample SAM API"
+  version: "v1.0"
+  contact:
+    email: [email protected]
+
+servers:
+  - url: https://hello.mydomain.com
+    description: Sample SAM API
+
+x-amazon-apigateway-request-validator: all
+x-amazon-apigateway-request-validators:
+  all:
+    validateRequestBody: true
+    validateRequestParameters: true
+
+x-amazon-apigateway-cors:
+  allowOrigins:
+    - "*"
+  allowMethods:
+    - "OPTIONS"
+    - "GET"
+  allowHeaders:
+    - "Content-Type"
+
+components:
+  schemas:
+    HelloResponse:
+      type: object
+      properties:
+        message:
+          type: string
+  examples:
+    HelloResponse:
+      summary: An example of hello message
+      value:
+        message: "Hello World!"
+
+tags:
+  - name: Hello
+
+paths:
+  /hello/{name}:
+    get:
+      operationId: sayHello
+      tags:
+        - Hello
+      summary: Say hello
+      description: Returns a greeting message
+      parameters:
+        - in: path
+          name: name
+          required: true
+          schema:
+            type: string
+          description: Your name
+      responses:
+        '200':
+          description: "OK"
+          content:
+            application/json:
+              schema:
+                $ref: "#/components/schemas/HelloResponse"
+              examples:
+                address_response:
+                  $ref: "#/components/examples/HelloResponse"
+        '400':
+          description: "Bad Request"
+        '500':
+          description: "Internal Server Error"
+      x-amazon-apigateway-integration:
+        passthroughBehavior: when_no_match
+        httpMethod: POST
+        type: aws_proxy
+        uri:
+          Fn::Sub: "arn:aws:apigateway:${AWS::Region}:lambda:path/2015-03-31/functions/${HelloWorldFunction.Arn}/invocations"
+        credentials:
+          Fn::Sub: "arn:aws:iam::${AWS::AccountId}:role/apigateway-invoke-lambda-role"