15 lines
1.3 KiB
Markdown
15 lines
1.3 KiB
Markdown
---
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id: technical-details
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title: Technical Details
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---
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This printer is a fork of [recast](https://github.com/benjamn/recast)’s printer with its algorithm replaced by the one described by Wadler in "[A prettier printer](https://homepages.inf.ed.ac.uk/wadler/papers/prettier/prettier.pdf)". There still may be leftover code from recast that needs to be cleaned up.
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The basic idea is that the printer takes an AST and returns an intermediate representation of the output, and the printer uses that to generate a string. The advantage is that the printer can "measure" the IR and see if the output is going to fit on a line, and break if not.
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This means that most of the logic of printing an AST involves generating an abstract representation of the output involving certain commands. For example, `["(", line, arg, line, ")"]` would represent a concatenation of opening parens, an argument, and closing parens. But if that doesn’t fit on one line, the printer can break where `line` is specified.
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The [Playground](https://prettier.io/playground) has a special mode for exploring how Prettier’s intermediate representation is printed. To get there, open the sidebar (the "Show options" button) and set the `parser` option to the special value `doc-explorer`.
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More (rough) details can be found in [commands.md](https://github.com/prettier/prettier/blob/main/commands.md).
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