syntax error, unexpected |=, expecting '}' - jq

Question

I want to build a json with jq filter, the usecase is very simple,
I have a json file as this,
# cat input.json
{"foo": 42, "bar": "less interesting data"}
and I want to generate a json file with jq as follow,
output:
increase the value of foo,
[
{
"leafCalls": {
"text": 43
}
}
]
and the filter I am using is defined as this,
# cat results.jq
[.[] | . as { foo: $leafText, bar: $leafCode} | {
leafCall: {
text: $leafText
},
} | {
leafCalls: .leafCall |= . + 1
}]
But there is a syntax issue as said below,
# <input.json jq --slurp --from-file results.jq > output.json
jq: error: syntax error, unexpected |=, expecting '}' (Unix shell quoting issues?) at <top-level>, line 6:
leafCalls: .leafCall |= . + 1
jq: 1 compile error
Beside, there is also a problem if want to concat a string to the value of "bar",
For what I want is,
[
{
"leafCalls": {
"text": "less interesting data string"
}
}
]
The filter is
# cat results2.jq
[.[] | . as { foo: $leafText, bar: $leafCode} | {
leafCall: {
text: $leafCode },
} | {
leafCalls: .leafCall + " " + "string"
}]
and the jq is saying,
jq: error: syntax error, unexpected '+', expecting '}'
Can anyone tell what's the problem with the filter definition?

Answer 1

To get the first output, increase the value directly. Parentheses are needed for precedence.
jq '[. as { foo: $leafText } | {
leafCalls: {
text: ($leafText + 1)
},
}
]' input.json
And similarly for the string:
jq '[ . as { foo: $leafText, bar: $leafCode}
| { leafCalls: { text: ($leafCode + " string" ) } } ]
' input.json