AWS SAM local start-api cannot resolve Fn::ImportValue

Question

I have SAM template (post here partially):

AWSTemplateFormatVersion: "2010-09-09"
Transform: "AWS::Serverless-2016-10-31"

Parameters:

  StorageStackName:
    Type: String
    Description: Name of the stack which provisions DynamoDB table and S3 bucket.

Globals:

  Function:
      Runtime: nodejs12.x
      MemorySize: 128
      Timeout: 8
      CodeUri: .
      AutoPublishAlias: latest
      Environment:
        Variables:
          SOURCE_TABLE_NAME:
            Fn::ImportValue:
              Fn::Sub: "${StorageStackName}-SourceTableName"

Command gives me a notification

sam local start-api --debug --parameter-overrides='StorageStackName=storage-dev'

Unable to resolve property SOURCE_TABLE_NAME: OrderedDict([('Fn::ImportValue', OrderedDict([('Fn::Sub', '${StorageStackName}-SourceTableName')]))]). Leaving as is.

I tried to remove Sub (no luck):

SOURCE_TABLE_NAME:
  Fn::ImportValue: "storage-dev-SourceTableName"

The template works on the server, so Fn::ImportValue supported. So my question is Fn::ImportValue supported in local invocation at all?

I am made sure I use same credentials (profile) for local SAM as the one where I have storage-dev stack. Any way I can recheck it again to make sure even more?

Answer 1

It looks like as of this post it is not supported. The last PR I could find only included !Sub and !If. Looks like they will have to be passed in as parameters or env variables while the sam cli matures.

Answer 2

It is a SAM bug that I hope gets fixed soon also. For now, I created a workaround. It is a bash file that gets the exported output value from another stack and passes it as an env variable during invocation, so it will be overwritten.

Just substitute the EXPORTED_VARIABLE_NAME and S3_BUCKET_NAME for your actual names and you are good to go.

Run it like so: ./sam_local_invoke.sh

#!/bin/bash

# The exported variable name from another stack (change it with your variable name)
EXPORTED_VARIABLE_NAME=BotsDataBucketSAM

# Get it as the name of the parameter that we want to overwrite
S3_BUCKET_NAME=$(aws cloudformation list-exports --query "Exports[?Name=='$EXPORTED_VARIABLE_NAME'].Value" --output text | cat)

ENV_OVERWRITES=$(cat <<EOT
{
  "Parameters": {
    "S3_BUCKET_NAME": "$S3_BUCKET_NAME"
  }
}
EOT
)

echo ${ENV_OVERWRITES} > env.json

sam local invoke --env-vars env.json