In the UK Community Slack #gutenberg channel Dan Atrill reported a problem with unwanted paragraphs.
I thought I'd already resolved this problem as reported in #20.

• I'd removed wpautop() processing from template-part.php
• And a fix has been developed for Gutenberg. But it isn't yet in a released version; it's wasn't in 10.4.0

While investigating a problem with the site logo image size I noticed the unexpected paragraph problem reappear in my page-footer template part. There were empty paragraphs around generated shortcode content.
For this particular problem I discovered a simple workaround. Change from using the wp:shortcode block to the custom HTML block. wp:html

I achieved this without having to look deeply into the code.
Instead I developed a custom template that displays the minimum output to debug the generated HTML.

This issue is to formally document the requirements for a custom template to help debug blocks in the front end.

Requirements

• To be able to visually check that blocks display the expected HTML
• To see both the formatted output and the original HTML for the block
• To provide a little styling to highlight paragraphs and other tags that can often appear unexpectedly and which throw off the expected styling.

Proposed solution

• Custom template called Output Input Debugging configured as below.
• Minimum amount of HTML in the template to go wrong
• Display the raw source of the contents of the post as escaped HTML
• Use the [contents] shortcode initially.
• Show WordPress and Gutenberg versions
• And a link back to home.
• Optionally style paragraphs and divs with unexpected borders to help spot these unwanted tags.

Custom template definition

{
      "name": "output-input",
      "title": "Output Input Debugging",
      "postTypes": [
        "page",
        "post",
        "block",
        "block_example"
      ]
    }

input-output.html is

<!-- wp:post-title /-->
<!-- wp:post-content /-->
<!-- wp:template-part {"slug":"contents-shortcode","theme":"fizzie"} /-->

contents-shortcode.html template part is

[contents]
[guts]
[bw_wpadmin]

<!-- wp:oik-css/css {"css":"p { border: 1px solid red; }\nbr { background: #eee; padding: 0px; content: \u0022A\u0022 !important;\n    display: block !important; border: 1px red dotted;}    ","text":"Problems? "} /-->

where

• [contents] is a shortcode from oik-block
• [guts] is a shortcode from oik-blocks
• [bw_wpadmin] is a shortcode from oik
• and the oik-css/css block is from oik-css.

All of which are needed on the site for which Fizzie is targetted.