feat: allow setting a lambda version description from S3 Metadata (#179)

Co-authored-by: Moritz do Rio Schulze <mdorioschulze@stroer.de>

Author: FrontierPsychiatrist

examples/deployment/complete/README.md

@@ -22,9 +22,12 @@ Note that this example may create resources which cost money. Run `terraform des
 Upload a new `zip` package to S3 to start the deployment pipeline:
 
 ```shell
-aws s3api put-object --bucket example-ci-{account_id}-{region} --key deployment-hooks/package/lambda.zip --body lambda.zip
+aws s3api put-object --bucket example-ci-{account_id}-{region} --key deployment-hooks/package/lambda.zip --metadata description="Description for the new Lambda version" --body lambda.zip
 ```
 
+The `--metadata description=` is optional. If set, it will use the value as the description for the new Lambda function
+version.
+
 <!-- BEGIN_TF_DOCS -->
 ## Requirements
 

examples/deployment/s3/README.md

@@ -16,9 +16,12 @@ Note that this example may create resources which cost money. Run `terraform des
 Upload a new `zip` package to S3 to start the deployment pipeline:
 
 ```shell
-aws s3api put-object --bucket example-ci-{account_id}-{region} --key s3-deployment/package/lambda.zip --body lambda.zip
+aws s3api put-object --bucket example-ci-{account_id}-{region} --key s3-deployment/package/lambda.zip --metadata description="Description for the new Lambda version" --body lambda.zip
 ```
 
+The `--metadata description=` is optional. If set, it will use the value as the description for the new Lambda function
+version.
+
 <!-- BEGIN_TF_DOCS -->
 ## Requirements
 

modules/deployment/README.md

@@ -181,6 +181,10 @@ of the CodePipeline needs an AWS S3 Notification for emitting events in your Ama
 filtered events to EventBridge and trigger the pipeline (see [docs](https://docs.aws.amazon.com/AmazonS3/latest/userguide/EventBridge.html) for details). Make sure to enable S3 bucket
 notifications for your source bucket!
 
+Optionally, if the S3 object being deployed has the metadata `description` set, it will be used as the description of
+the new published version of the Lambda, truncated at 256 characters. You are responsible for setting this metadata when
+you produce the object in S3. Without the metadata, the function description is copied for the version description.
+
 ### with custom deployment configuration
 
 This module supports all predefined [default deployment configurations](https://docs.aws.amazon.com/codedeploy/latest/userguide/deployment-configurations.html)

modules/deployment/codebuild.tf

@@ -103,8 +103,21 @@ phases:
           versionId = os.environ.get("SOURCEVARIABLES_VERSIONID")
           print(f"S3 deployment: {s3_bucket}/{s3_key} (versionId={versionId})")
 
-          update_response = lambda_client.update_function_code(FunctionName=lambda_function_name, S3Bucket=s3_bucket, S3Key=s3_key, S3ObjectVersion=versionId, Publish=True)
-          target_version = update_response["Version"]
+          s3_client = boto3.client("s3", region_name=os.environ.get("REGION"))
+          s3_attributes = s3_client.head_object(Bucket=s3_bucket, Key=s3_key, VersionId=versionId)
+
+          if "description" in s3_attributes["Metadata"]:
+            description = s3_attributes["Metadata"]["description"]
+            # The description of a lambda version can be max 256 characters, so we need to ensure that here
+            truncated_description = description[:256]
+            update_response = lambda_client.update_function_code(FunctionName=lambda_function_name, S3Bucket=s3_bucket, S3Key=s3_key, S3ObjectVersion=versionId, Publish=False)
+            waiter = lambda_client.get_waiter("function_updated_v2")
+            waiter.wait(FunctionName=lambda_function_name)
+            publish_response = lambda_client.publish_version(FunctionName=lambda_function_name, CodeSha256=update_response["CodeSha256"], Description=truncated_description)
+            target_version = publish_response["Version"]
+          else:
+            update_response = lambda_client.update_function_code(FunctionName=lambda_function_name, S3Bucket=s3_bucket, S3Key=s3_key, S3ObjectVersion=versionId, Publish=True)
+            target_version = update_response["Version"]
         else:
           # ECR/image deployment
           image_uri = os.environ.get("SOURCEVARIABLES_IMAGE_URI")