Motivation

Sometimes I want to use templates (for example, Mustache) that are a little complicated, and some formatting helps readability (this often happens in conjunction with SBError messages, for example). Consider:

const message = `
    {{#context}}
        At {{context}}, found
    {{/context}}
    {{^context}}
        Found
    {{/context}}
    
    {{problem}}.
`;

The trouble is, even using an identation-trimmer, this yields unwanted whitespace:

At someplace, found

there was a problem.

This formatter takes "gross" template output and provides reasonable formatting:

At someplace, found there was a problem.

Usage

const condense = require('@shieldsbetter/condense-template-whitespace');
const Mustache = require('mustache');

console.log(condense(Mustache.render(`
    {{#context}}
        At {{context}}, found
    {{/context}}
    {{^context}}
        Found
    {{/context}}
    
    {{problem}}.
`, {
    context: 'someplace',
    problem: 'found there was a problem'
})));

// Output: 'At someplace, found there was a problem.'

Algorithm

Whitespace is defined to be spaces, tabs, and newlines.

Leading and trailing whitespace is trimmed.

Internal consecutive blocks of whitespace are replaced by a single space, except in the case that the whitespace block contains multiple blank lines, in which case it will be replaced with a number of newlines equal to the number of contained blank lines minus one.

So:

console.log(condense(`
    Sometimes
    
    you
    
    
    want
    
    
    
    newlines.
`));

// Output:
//   Sometimes you
//   
//   want
//   
//   
//   newlines.