View Source Styler.Style behaviour (Styler v0.5.1)

A Style takes AST and returns a transformed version of that AST.

Because these transformations involve traversing trees (the "T" in "AST"), we wrap the AST in a structure called a Zipper to facilitate walking the trees.

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Callbacks

run will be used with Zipper.traverse_while/3, meaning it will be executed on every node of the AST.

Functions

Deletes :line from the node's meta

Set the line of all comments with line in range_start..range_end to instead have line range_start

Ensure the parent node can have multiple children.

Change the line of all comments with line in range by adding delta to it. A positive delta will move the lines further down a file, while a negative delta will move them up.

Link to this section Types

@type context() :: %{comment: [map()], file: :stdin | String.t()}

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run will be used with Zipper.traverse_while/3, meaning it will be executed on every node of the AST.

You can skip traversing parts of the tree by returning a Zipper that's further along in the traversal, for example by calling Zipper.skip(zipper) to skip an entire subtree you know is of no interest to your Style.

Link to this section Functions

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delete_line_meta(ast_node)

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Deletes :line from the node's meta

If you expected {:foo, foo_meta, [bar, baz, bop] to give you a a single line like

foo(bar, baz, bop)

but instead got

foo(

bar,
baz,
bop

)

then it's likely that at least one of bar, baz, and/or bop have :line meta that's confusing the formatter and causing the multilining.

This function fixes that problem.

# => foo(bar, baz, bop)

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displace_comments(comments, range)

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Set the line of all comments with line in range_start..range_end to instead have line range_start

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ensure_block_parent(zipper)

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Ensure the parent node can have multiple children.

If a context-changing node (a do end block or an -> arrow block) is encountered the child is wrapped in a :__block__

Other nodes (pipes, assignments) can only have a fixed number of children. This function will recursively traverse up the zipper until it's found the parents of those nodes.

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shift_comments(comments, range, delta)

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Change the line of all comments with line in range by adding delta to it. A positive delta will move the lines further down a file, while a negative delta will move them up.