efdba79ad1
New templates variables can be added by giving variable-value pairs as a
second return value of the global function `Doc`.
Example:
function Doc (body, meta, vars)
vars.date = vars.date or os.date '%B %e, %Y'
return body, vars
end
Closes: #6731
68 lines
1.6 KiB
Markdown
68 lines
1.6 KiB
Markdown
---
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author:
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- John MacFarlane
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date: 'November 21, 2021'
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title: Creating Custom Pandoc Writers in Lua
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---
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# Introduction
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If you need to render a format not already handled by pandoc,
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or you want to change how pandoc renders a format,
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you can create a custom writer using the [Lua] language.
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Pandoc has a built-in Lua interpreter, so you needn't
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install any additional software to do this.
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[Lua]: https://www.lua.org
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A custom writer is a Lua file that defines functions for
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rendering each element of a pandoc AST.
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For example,
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``` lua
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function Para(s)
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return "<paragraph>" .. s .. "</paragraph>"
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end
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```
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The best way to go about creating a custom writer is to modify
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the example that comes with pandoc. To get the example, you
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can do
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```
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pandoc --print-default-data-file sample.lua > sample.lua
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```
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# A custom HTML writer
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`sample.lua` is a full-features HTML writer, with explanatory
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comments. To use it, just use the path to the custom writer as
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the writer name:
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```
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pandoc -t sample.lua myfile.md
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```
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`sample.lua` defines all the functions needed by any custom
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writer, so you can design your own custom writer by modifying
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the functions in `sample.lua` according to your needs.
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``` {.lua include="sample.lua"}
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```
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# Template variables
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New template variables can be added, or existing ones
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modified, by returning a second value from function `Doc`.
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For example, the following will add the current date in
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variable `date`, unless `date` is already defined as either a
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metadata value or a variable:
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``` lua
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function Doc (body, meta, vars)
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vars.date = vars.date or meta.data or os.date '%B %e, %Y'
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return body, vars
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end
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```
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