How does aws_completer return its suggestions?

[gautaz]

Hello,

Looking at the bash documentation on how completion commands are added, the manual pages state the following for the -C argument of the bash builtin complete:

              -C command
                      command is executed in a subshell environment, and its output is used as the possible completions.  Arguments are passed as with the -F option.
              -F function
                      The  shell  function  function is executed in the current shell environment.  When the function is executed, the first argument ($1) is the name of the command whose arguments are being completed, the second argument ($2) is the word being com‐
                      pleted, and the third argument ($3) is the word preceding the word being completed on the current command line.  When it finishes, the possible completions are retrieved from the value of the COMPREPLY array variable.

As I am trying to understand how aws_completer returns its suggestions, I tried to directly call it with some arguments:

sh-4.2# aws_completer aws s aws

sh-4.2# aws_completer aws s3 aws

sh-4.2#

I was expecting aws_completer to output the same suggestions that can be obtained after complete -C aws_completer aws is executed:

sh-4.2# aws s
s3                              s3outposts                      sagemaker-edge                  sagemaker-metrics               scheduler                       secretsmanager                  serverlessrepo                  servicecatalog-appregistry      sesv2                           simspaceweaver                  snowball                        ssm                             ssm-sap                         sso-oidc                        sts                             swf
s3api                           sagemaker                       sagemaker-featurestore-runtime  sagemaker-runtime               schemas                         securityhub                     service-quotas                  servicediscovery                shield                          sms                             sns                             ssm-contacts                    sso                             stepfunctions                   support                         synthetics
s3control                       sagemaker-a2i-runtime           sagemaker-geospatial            savingsplans                    sdb                             securitylake                    servicecatalog                  ses                             signer                          snow-device-management          sqs                             ssm-incidents                   sso-admin                       storagegateway                  support-app
sh-4.2# aws s3
s3          s3api       s3control   s3outposts
sh-4.2# aws s3

But this does not seem to be the case.

Would anyone shed some light on this?