Add Lint/Typos rule

.ameba.yml

@@ -1,3 +1,7 @@
 Lint/DocumentationAdmonition:
   Timezone: UTC
   Admonitions: [FIXME, BUG]
+
+Lint/Typos:
+  Excluded:
+  - spec/ameba/rule/lint/typos_spec.cr

.github/workflows/ci.yml

@@ -32,6 +32,10 @@ jobs:
       - name: Install dependencies
         run: shards install
 
+      - name: Install typos-cli
+        if: matrix.os == 'macos-latest'
+        run: brew install typos-cli
+
       - name: Run specs
         run: crystal spec
 

spec/ameba/rule/lint/typos_spec.cr

@@ -0,0 +1,32 @@
+require "../../../spec_helper"
+
+private def check_typos_bin!
+  unless Ameba::Rule::Lint::Typos::BIN_PATH
+    pending! "`typos` executable is not available"
+  end
+end
+
+module Ameba::Rule::Lint
+  subject = Typos.new
+    .tap(&.fail_on_error = true)
+
+  describe Typos do
+    it "reports typos" do
+      check_typos_bin!
+
+      source = expect_issue subject, <<-CRYSTAL
+        # method with no arugments
+                       # ^^^^^^^^^ error: Typo found: arugments -> arguments
+        def tpos
+          # ^^^^ error: Typo found: tpos -> typos
+        end
+        CRYSTAL
+
+      expect_correction source, <<-CRYSTAL
+        # method with no arguments
+        def typos
+        end
+        CRYSTAL
+    end
+  end
+end

src/ameba/rule/lint/typos.cr

@@ -0,0 +1,96 @@
+module Ameba::Rule::Lint
+  # A rule that reports typos found in source files.
+  #
+  # NOTE: Needs [typos](https://github.com/crate-ci/typos) CLI tool.
+  # NOTE: See the chapter on [false positives](https://github.com/crate-ci/typos#false-positives).
+  #
+  # YAML configuration example:
+  #
+  # ```
+  # Lint/Typos:
+  #   Enabled: true
+  #   BinPath: ~
+  #   FailOnError: false
+  # ```
+  class Typos < Base
+    properties do
+      description "Reports typos found in source files"
+      bin_path nil.as(String?)
+      fail_on_error false
+    end
+
+    MSG = "Typo found: %s -> %s"
+
+    BIN_PATH = Process.find_executable("typos")
+
+    def bin_path : String?
+      @bin_path || BIN_PATH
+    end
+
+    def test(source : Source)
+      typos = typos_from(source)
+      typos.try &.each do |typo|
+        corrections = typo.corrections
+        message = MSG % {
+          typo.typo, corrections.join(" | "),
+        }
+        if corrections.size == 1
+          issue_for typo.location, typo.end_location, message do |corrector|
+            corrector.replace(typo.location, typo.end_location, corrections.first)
+          end
+        else
+          issue_for typo.location, typo.end_location, message
+        end
+      end
+    rescue ex
+      raise ex if fail_on_error?
+    end
+
+    private record Typo,
+      path : String,
+      typo : String,
+      corrections : Array(String),
+      location : {Int32, Int32},
+      end_location : {Int32, Int32} do
+      def self.parse(str) : self?
+        issue = JSON.parse(str)
+
+        return unless issue["type"] == "typo"
+
+        typo = issue["typo"].as_s
+        corrections = issue["corrections"].as_a.map(&.as_s)
+
+        return if typo.empty? || corrections.empty?
+
+        path = issue["path"].as_s
+        line_no = issue["line_num"].as_i
+        col_no = issue["byte_offset"].as_i + 1
+        end_col_no = col_no + typo.size - 1
+
+        new(path, typo, corrections,
+          {line_no, col_no}, {line_no, end_col_no})
+      end
+    end
+
+    protected def typos_from(source : Source) : Array(Typo)?
+      unless bin_path = self.bin_path
+        if fail_on_error?
+          raise RuntimeError.new "Could not find `typos` executable"
+        end
+        return
+      end
+      status = Process.run(bin_path, args: %w[--format json -],
+        input: IO::Memory.new(source.code),
+        output: output = IO::Memory.new,
+      )
+      return if status.success?
+
+      ([] of Typo).tap do |typos|
+        # NOTE: `--format json` is actually JSON Lines (`jsonl`)
+        output.to_s.each_line do |line|
+          Typo.parse(line).try { |typo| typos << typo }
+        end
+      end
+    end
+  end
+end