Terraform external data source formatting issue - amazon-web-services

Question

I want a list of my s3 buckets in TF.
With the AWS CLI I can get that list and format it into JSON:
my-mac$ eval aws s3 ls | awk '{print $3}' | jq -R -s -c 'split("\n")' | jq '.[:-1]'
[
"xxx-bucket-1",
"xxx-bucket-2"
]
But TF won't fetch it, and it's driving me mad.
Here's my data source config:
data "external" "bucket_objects" {
program = ["bash", "cli.sh"]
}
The shell script file contents:
#!/bin/bash
set -e
eval aws s3 ls | awk '{print $3}' | jq -R -s -c 'split("\n")' | jq '.[:-1]'
And finally, the error message:
│ Error: Unexpected External Program Results
│
│ with data.external.bucket_objects,
│ on data.tf line 22, in data "external" "bucket_objects":
│ 22: program = ["bash", "cli.sh"]
│
│ The data source received unexpected results after executing the program.
│
│ Program output must be a JSON encoded map of string keys and string values.
│
│ If the error is unclear, the output can be viewed by enabling Terraform's
│ logging at TRACE level. Terraform documentation on logging:
│ https://www.terraform.io/internals/debugging
│
│ Program: /bin/bash
│ Result Error: json: cannot unmarshal array into Go value of type
│ map[string]string
My shell scripting game is weak and it's going to be something dumb, but I don't know what that is.

Answer 1

Here is an example that worked in my case:
#!/bin/bash
set -e
BUCKET_NAMES=$(aws s3 ls | awk '{print $3}' | jq -R -s -c 'split("\n")' | jq '.[:-1]')
jq -n --arg bucket_names "$BUCKET_NAMES" '{"bucket_names":$bucket_names}'