SAM CLI - Unable to build - amazon-web-services

Question

I have a project set up for SAM that I cannot assume was correctly set up.
When I try to run sam build --use-container, this happens:
>sam build --use-container
Starting Build inside a container
Building codeuri: /...whatever.../hello_world runtime: python3.7 metadata: {} functions: ['HelloWorldFunction']
Fetching public.ecr.aws/sam/build-python3.7:latest Docker container image......
Mounting /...whatever.../hello_world as /tmp/samcli/source:ro,delegated inside runtime container
Build Failed
Running PythonPipBuilder:ResolveDependencies
Error: PythonPipBuilder:ResolveDependencies - Requirements file not found: /tmp/samcli/source/requirements.txt
I'm not surprised that it can't find /tmp/samcli/source/requirements.txt, because it does not exist. Instead, I would expect it to look in ./main/requirements.txt, which is there.
Here is my template file:
AWSTemplateFormatVersion: '2010-09-09'
Transform: AWS::Serverless-2016-10-31
Description: >
my-service
Globals:
Function:
Timeout: 3
Resources:
HelloWorldFunction:
Type: AWS::Serverless::Function
Properties:
CodeUri: hello_world/
Handler: app.lambda_handler
Runtime: python3.7
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
What could be the reason for this error?

Answer 1

The location of requirements.txt is based on the CodeUri location in the template.
Based on your template, sam build command is expecting it under hello_world/ directory.
Since it cannot find in that location, it's looking under the mounted directory /tmp/samcli/source
Provide requirements.txt in the location specified in CodeUri (hello_world/) in the template to resolve the issue.