44 lines
1006 B
Crystal
44 lines
1006 B
Crystal
require "./base"
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module Ameba::Rule::Performance
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# This rule is used to identify usage of `flatten` calls that follow `map`.
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#
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# For example, this is considered inefficient:
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#
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# ```
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# %w[Alice Bob].map(&.chars).flatten
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# ```
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#
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# And can be written as this:
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#
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# ```
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# %w[Alice Bob].flat_map(&.chars)
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# ```
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#
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# YAML configuration example:
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#
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# ```
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# Performance/FlattenAfterMap:
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# Enabled: true
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# ```
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class FlattenAfterMap < Base
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properties do
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description "Identifies usage of `flatten` calls that follow `map`"
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end
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MSG = "Use `flat_map {...}` instead of `map {...}.flatten`"
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def test(source)
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AST::NodeVisitor.new self, source, skip: :macro
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end
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def test(source, node : Crystal::Call)
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return unless node.name == "flatten" && (obj = node.obj)
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return unless obj.is_a?(Crystal::Call) && obj.block
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return unless obj.name == "map"
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issue_for obj.name_location, node.name_end_location, MSG
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end
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end
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end
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