Use mermaid.render() instead of mermaid.run() API to avoid removing whitespace from diagrams
#536
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The current regex match group we're using to get the mermaid diagrams from markdown prepends a `\n` character to every mermaid diagram. This only currently works because the current mmdc -> HTML -> mermaid.init step removes these newlines automatically.
Currently, `mermaid-cli` renders mermaid diagrams by: mmd code → HTML `<div>` contexts → mermaid.run() → HTML `<svg>` However, when converting the mmd code to HTML `<div>`, newlines and whitespace formatting may get removed. For the majority of diagrams, this is no issue, but for some diagrams (e.g. classDiagram), whitespace does matter. The mermaid API has a `mermaid.render()` function that we can use instead, which parses in mmd code directly, without having to go through a HTML element first: mmd code → mermaid.render() → SVG → HTML `<svg>` As an additional benefit, we get better error messages from Mermaid (they're now proper JavaScript `Error`s!) Fixes: mermaid-js#532
aloisklink
commented
May 4, 2023
| @@ -449,7 +416,7 @@ async function run (input, output, { puppeteerConfig = {}, quiet = false, output | |||
| if (input && /\.(md|markdown)$/.test(input)) { | |||
| const imagePromises = [] | |||
| for (const mermaidCodeblockMatch of definition.matchAll(mermaidChartsInMarkdownRegexGlobal)) { | |||
| const mermaidDefinition = mermaidCodeblockMatch[1] | |||
| const mermaidDefinition = mermaidCodeblockMatch[2] | |||
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The bug here was the regex has two match groups, where Group 1 contains a leading newline! Group 2 is the correct group to use, since it doesn't contain the \n character.
Normally, when using HTML, you can put as many newlines as you want and the browser will remove everything (so this bug didn't matter), but the mermaid.render() API is much stricter.
See
|
Brilliant work! I appreciate your help very much! |
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📑 Summary
Use the
mermaid.render()function instead of themermaid.run()function to parse Mermaid diagram definitions directly, without going through HTML first.📏 Design Decisions
Currently,
mermaid-clirenders mermaid diagrams by:flowchart LR subgraph a ["Removes newlines!!!"] div["HTML <div>"] end MMD --> div["HTML <div>"] div -->|"mermaid.run()"| svg["HTML <svg>"]However, when converting the mmd code to HTML
<div>, newlines and whitespace formatting may get removed. For the majority of diagrams, this is no issue, but for some diagrams (e.g.classDiagram), whitespace does matter.The mermaid API has a
mermaid.render()function that we can use instead, which parses in mmd code directly, without having to go through a HTML element first:flowchart LR MMD -->|"mermaid.render()"| svgText["SVG text"] -->svg["HTML <svg>"]As an additional benefit, we get better error messages from Mermaid too!
📋 Tasks
Make sure you
masterbranch