Why is the first line is skipped

Why is the first line skipped if I remove echo "prevent remove first line"?

(echo "prevent remove first line" && find ~/somedir -mindepth 1 -maxdepth 1 -type d) | /usr/local/bin/jq -nR \
'{
    "items": [
        inputs |                                     
        inputs as $title |                  
        {
            "title": $title,
        }
    ]
}'

>Solution :

Your example should be:

find ~/somedir -mindepth 1 -maxdepth 1 -type d | /usr/local/bin/jq -nR \
'{
    "items": [      
        inputs as $title |                  
        {
            "title": $title,
        }
    ]
}'

From the jq man page:

 inputs
       Outputs all remaining inputs, one by one.

       This is primarily useful for reductions over a program´s inputs.

This implicitly means that every time called, inputs reads the next line from stdin. stdin is realized as a pipe, once a line from stdin has been read, it is gone.

When you echo a line before the actual input, then this extra line will be subject to this extra read. Just use inputs twice to see the problem coming back:

(echo "test" && find ~/somedir -mindepth 1 -maxdepth 1 -type d) | /usr/local/bin/jq -nR \
'{
    "items": [
        inputs | inputs |
        inputs as $title |                  
        {
            "title": $title,
        }
    ]
}'

PS: As pmf pointed out, the whole solution can be simplified to:

find ~/somedir -mindepth 1 -maxdepth 1 -type d \
    jq -nR '{items: [{title: inputs}]}'