Set key with value on a line in a file, if not exists between specific lines, or set specific value

Question

Given the following configuration file:

    shape {
        visible: true
        type: rectangle
        ...
    }
    
    shape {
        type: circle
        visible: isRound === "true"
        ...
    }
    
    shape {
        // comment: "visible" not set, default "true" 
    }

How to set using bash all the values for visible key (property) to false, without touching the comments, but keeping the old value as a comment? The new content should be:

    shape {
        visible: false
        type: rectangle
        ...
    }
    
    shape {
        type: circle
        visible: false // visible: isRound === "true"
        // ideally, above, the old value is kept as a comment...
        ...
    }
    
    shape {
        visible: false
        // comment: "visible" not set, default "true" 
    }

The file is not just a list of shape structures, may contain other entries too. This should be QML compliant.

awk shows:

awk --version
GNU Awk 5.2.1, API 3.2
Copyright (C) 1989, 1991-2022 Free Software Foundation.

Edit

I think I can use this PCRE regex:

(\s*shape\s*\{\n)(\s*)(.*?)(visible\:.*\n?)?(.*?)(\n\s*\})

with replace expression as:

$1$2visible: false // $4\n$2$5$6

or

\1\2visible: false // \4\n\2\5\6

but I need a tool to apply it. It is not perfect, still needs to not comment twice.

Answer 1

I'd use perl for this kind of thing:

perl -0777 -pe '
  s{shape\s*\{.*?\}}{
    $& =~ s{(//.*)|\b(visible:\s*+)(?!true\s*$).*}{$1 ? $1 : "${2}true // $&"}gmre
  }gse' your-file

Answer 2

awk -v key='visible:' -v value='false' '
    /{/ {
        found=0 # reset flag
    }
    $1==key {
        found=1 # set flag
        
        # change true to value
        if ($2=="true") { sub($2, value, $0) }

        # if not value, replace property with key-value and comment
        else if ($2!=value) { sub($1, $1 " " value " // " $1, $0) }
    }
    /}/ && !found {
        # get indentation of }
        indent=$0; sub(/}.*/, "", indent)
        
        # insert property
        print indent indent key " " value
    }
    { print }
' file

There must not be any other opening { or closing } in your properties/comments or the insertion won't work. They must also occur on separate lines.

A missing property is inserted before the closing } and the indentation is set to two times the indentation of }. I'm not sure if this will be always correct or how to determine it (two tabs?).

If a property already has the right value, it is left untouched.

If you don't want to repeat the property name in comments, change the command to sub($1, $1 " " value " //", $0). The result would be visible: false // isRound === "true".

Output:

    shape {
        visible: false
        type: rectangle
        ...
    }
    
    shape {
        type: circle
        visible: false // visible: isRound === "true"
        ...
    }
    
    shape {
        // comment: "visible" not set, default "true" 
        visible: false
    }