sed to convert from multiline to single does not work - bash

Question

I am working on a shell script that would read filenames based on a topic name, read the file content, convert the text to a single line and post the message to kafka using kafka consumer.
For converting the contents of the json file, I am trying to use sed and seen many examples and tried them all. But none of them seem to convert the multiline text to single line so I could use it to post to kafka topic
This is the script I am trying to write
declare -A topicconfig
while read -r topic configfile; do
topicconfig["$topic"]="$configfile"
done <config_params.txt
for topic in "${!topicconfig[#]}"; do
echo "filename : ${topicconfig[$topic]}"
textFromFile=$(sed -e 's/[\n|\r]$//g' "${topicconfig[$topic]}")
echo "textFromFile : $textFromFile"
/bin/kafka-console-producer --bootstrap-server=${BOOTSTRAP_SERVER} \
--producer.config ~/client.properties --topic ${topic} <<< "${textFromFile}"
echo "configuration added to $topic"
done
What would be the reason sed doesn't convert the string to single line? Or how else could I change the call to sed to achieve the conversion from multiline to a single line?
The sed version is
Thank you
UPDATE
Sample Input
{
"eventType": "Dashboard_Configuration",
"version": 1,
"environments": [
"dev",
"qa",
"stage",
"prod"
],
"events": [
{
"sourceSystem": "FINTRX",
"events": [
{
"parentEventName": "Benefit",
"stageCount": 3,
"stages": [
{
"order": 1,
"stageName": "IngestStage",
"stageType": "INGEST"
},
{
"order": 2,
"stageName": "AvroStage",
"stageType": "AVRO"
},
{
"order": 3,
"stageName": "ReconciliationStage",
"stageType": "RECONCILIATION"
}
]
}
]
}
]
}
Expected Output
{ "eventType": "Dashboard_Configuration", "version": 1, "environments": [ "dev", "qa", "stage", "prod" ], "events": [ { "sourceSystem": "FINTRX", "events": [ { "parentEventName": "Policy Financial Transaction", "stageCount": 3, "stages": [ { "order": 1, "stageName": "IngestStage", "stageType": "INGEST" }, { "order": 2, "stageName": "AvroStage", "stageType": "AVRO" }, { "order": 3, "stageName": "ReconciliationStage", "stageType": "RECONCILIATION" } ] } ] } ] }
The Actual Output
Same as input - for the last iteration - some other iteration it was dropping the r and n from the string - but putting it on one line
Thanks

Answer 1

sed is designed to work on lines, it wouldn't do a good job working across lines in most cases.
A much easier way to delete newlines is tr -d '\r\n':
$ printf "PRE"; printf "%s\n" a b c; printf "POST"; echo
PREa
b
c
POST
$ printf "PRE"; printf "%s\n" a b c | tr -d '\r\n'; printf "POST"; echo
PREabcPOST

Answer 2

You can use bash's built-in string search and replace to delete newline characters
# Delete any newline character
read -r -d '' textFromFile <"${topicconfig[$topic]}"
textFromFile="${textFromFile//[$'\n\r']/}"
Now if you want to replace newlines with a space using the same feature
shopt -s extglob # Needed for extended glob patterns
read -r -d '' textFromFile <"${topicconfig[$topic]}"
# Replace one or more newlines by a single space
textFromFile="${textFromFile//+([$'\n\r'])/ }"

Answer 3

Replace: (sed)
textFromFile=$(sed -e 's/[\n|\r]$//g' "${topicconfig[$topic]}")
With: (awk)
textFromFile=$(awk '{printf $0}' "${topicconfig[$topic]}")
With: (root's tr solution)
textFromFile=$(tr -d '\r\n' < "${topicconfig[$topic]}")
NOTE: Neither of these ideas deal with the management of 'extra' white space, eg, removing leading spaces/tabs in a line and replacing with a single space (as shown in OP's expected output)