astro/packages/astro/components/Debug.astro

---
const key = Object.keys(Astro.props)[0];
const value = Astro.props[key];

const getType = (node: unknown) => {
  if (Array.isArray(node)) return 'array';
  if (node === null) return 'null';
  if (typeof node === 'object') {
    if ((node as any).then) return 'promise';
  }
  return typeof node;
};

const getSummary = (node: any, key: string, className: string) => {
  const type = getType(node);
  let value;
  let open;
  let close;

  if (type === 'function') {
    return <>
      {(key || !key && key === 0) && <><span class={`${className} key`}>{key}</span><span class={`${className} sep`}>:</span></>}
      <span class={`${className} value value-function`}>{node.name}<span class={`${className} punc`}>()</span></span>
    </>
  }

  if (type === 'promise') {
    return <>
      {(key || !key && key === 0) && <><span class={`${className} key`}>{key}</span><span class={`${className} sep`}>:</span></>}
      <span class={`${className} value value-promise`}>Promise</span>
    </>
  }

  if (type === 'array') {
    value = node.length;
    open = <><span class={`${className} none`}>Array</span>{'['}</>;
    close = ']';
  } else if (type === 'object') {
    const keys = Object.keys(node);
    if (keys.length === 0) {
      value = 'Empty';
    } else if (keys.length > 3) {
      value = '…';
    } else {
      value = keys.slice(0, 3).join(',');
    }
    open = '{';
    close = '}';
  };

  return <>
    {key && <><span class={`${className} key`}>{key}</span>: </>}
    {open && <span class={`${className} punc`}>{open}</span>}
    <span class={`${className} hide`}>
      <span class={`${className} len`}>{value}</span>
      {close && <span class={`${className} punc`}>{close}</span>}
    </span>
  </>;
};

const Details = ({ node, key, children, class: className }) => {
  const type = getType(node);
  const props = {};

  if (type === 'array' || type === 'object') {
    props['data-char'] = type === 'array' ? ']' : '}'
    props.open = !key && type === 'object' ? '' : undefined;
  }
  
  return (
    <details {...props} class={className}>
        <Summary node={node} key={key} class={className} />
        {children}
    </details>
  );
}

const Summary = ({ node, key, class: className }) => {
  return (
    <summary class={className}>{getSummary(node, key, className)}</summary>
  );
}

const Empty = Symbol('Empty');

const KeyValue = ({ key, value, dim, class: className }) => {
  let type = key === '__proto__' ? 'prototype' : getType(value);
  if (type === 'null') {
    value = 'null';
  } else if (type === 'undefined') {
    value = 'undefined';
  } else if (value === Empty) {
    type = 'empty';
    value = 'Empty';
  } else {
    value = JSON.stringify(value);
  }

  return (
    <div class={`${className} line`}>
      {(key || !key && key === 0) && <><span class={`${className} key ${dim ? 'key-dim' : ''}`.trim()}>{key}</span><span class={`${className} sep`}>:</span></>}
      <span class={`${className} value value-${type}`}>
        {value}
      </span>
    </div>
  )
}

const Node = ({ node, key, class: className, ...props }) => {
  const type = getType(node);
  className = className.replace(/debug-value/g, '');

  if (type === 'array' || type === 'object') {
    let children = [];
    if (type === 'array' && node.length > 0 && Object.entries(node).length === 0) {
      children = Array.from({ length: node.length }, (_, key) => <Node node={Empty} key={key} class={className} />);
    } else {
      children = Object.entries(node).map(([key, value]) => <Node node={value} key={key} class={className} />);
    }
    return (
      <Details node={node} key={key} children={children} class={className} />
    );
  } else if (type === 'function') {
    return (
      <Details node={node} key={key} class={className} children={
      <>
        <KeyValue key="name" value={node.name} dim={true} class={className} />
        <KeyValue key="__proto__" value="Function" dim={true} class={className} />
      </>
      }/>
    );
  } else if (type === 'promise') {
    return (
      <Details node={node} key={key} class={className} children={
        <KeyValue key="__proto__" value="Promise" dim={true} />
      } />
    );
  }

  return <KeyValue key={key} value={node} class={className} />;
}
---

<div class="debug">
  <div class="debug-header">
    <h2 class="debug-title"><span class="debug-label">Debug</span> <span class="debug-name">"{key}"</span></h2>
  </div>

  <main>
    <Node node={value} class="debug-value" />
  </main>
</div>

<style lang="scss">
.debug-header {
  background: #FF1639;
  margin: -1rem -1.5rem 1rem;
  padding: 0.25rem 0.75rem;
}

.debug-title {
  font-size: 1em;
  color: #fff;
  margin: 0.5em 0;
}

.debug-label {
  font-weight: bold;
  text-transform: uppercase;
  margin-right: 0.75em;
}

.debug {
  all: initial;
  display: flex;
  flex-direction: column;
  padding: 1rem 1.5rem;
  overflow-y: hidden;
  overflow-x: auto;
  border: 1px solid #FFCFD6;

  background: #FFF;
  font-family: Consolas, "Andale Mono WT", "Andale Mono", "Lucida Console", "Lucida Sans Typewriter", "DejaVu Sans Mono", "Bitstream Vera Sans Mono", "Liberation Mono", "Nimbus Mono L", Monaco, "Courier New", Courier, monospace;
  font-size: 0.8rem;
  line-height: 1.44;
  color: #6b7280;
  white-space: pre;

}

details[open] > summary span.hide {
  visibility: hidden;
}

details[open] > summary span.none {
    display: none;
  }

details > details {
    padding-left: 1em;
  }

.line {
    padding-left: 1.125em;
  }

details[open]::after {
    content: attr(data-char);
  }

.sep {
    margin-right: 0.25em;
  }


details > summary {
    cursor: pointer;
  }

details:hover > summary::before,
details:focus > summary::before {
  transform: translate(0.25em, -0.25em);
}

details > summary::before {
  content: '';
  background-image: url("data:image/svg+xml,%3Csvg width='16' height='16' viewBox='0 0 16 16' fill='none' xmlns='http://www.w3.org/2000/svg'%3E%3Cpath d='M13 8L2.60769 14L2.6077 2L13 8Z' fill='%236B7280' /%3E%3C/svg%3E%0A");
  background-size: 1em;

  display: inline-flex;
  font-size: 0.5em;
  width: 1em;
  height: 1em;
  margin-right: 1.25em;
  margin-left: -2em;
  transform: translate(0, -0.25em);
  line-height: 1em;
  transition: transform 120ms ease-in;
}

details[open] > summary::before {
  transform: translate(0.25em, -0.25em) rotate(90deg);
}

.debug :global(::marker) {
  content: '';
  width: 0;
  visibility: hidden;
}

.key {
  color: #882de7;
}

.key-dim {
  color: #B881F1;
}

.len {
  color: #B881F1;
}

details:hover > summary,
details:focus > summary,
details:hover > summary .punc,
details:focus > summary .punc,
details:hover[open]::after,
details:focus[open]::after {
  color: #000012;
}

details:hover > summary .len,
details:focus > summary .len {
  color: #882DE7;
}

.punc {
  color: #6b7280;
}

.value-string {
  color: #17c083;
}

.value-function::before {
  content: 'ƒ ';
  color: #3894ff;
}
.value-function {
  color: #5076f9;
}

.value-number {
  color: #ff5d01;
}

.value-null,
.value-undefined {
  color: #9ca3af;
}

main > .line {
  margin-left: -0.75em;
  padding-left: 0;
}
</style>