[ruby/irb] Improve RubyLex's tests

(https://github.com/ruby/irb/pull/484)

* Improve assert_indenting helper

Instead of putting assertions inside the `auto_indent` block, we
can just make `auto_indent` return the calculated space count, and use
it for assertion outside of the `auto_indent` block call.

This simplifies the setup code and makes the intention easier to
understand.

* Introduce assert_row_indenting helper

1. Helper users shouldn't need to write 2 assertions for the current and
   the next line's indentation.
2. With this new approach, we can generate clearer error message for
   both cases:

When the current line's space count doesn't match

```
  Incorrect spaces calculation for line:

  ```
> def each_top_level_statement
  ```

  All lines:

  ```
  def each_top_level_statement
  ```

<0> expected but was
<nil>
```

When the next line's space count doesn't match

```
  Incorrect spaces calculation for line after the current line:

  ```
  def each_top_level_statement
>
  ```

  All lines:

  ```
  def each_top_level_statement
  ```

<3> expected but was
<2>
```

* Replace assert_indenting with assert_row_indenting

1 files changed, 71 insertions, 58 deletions

diff --git a/test/irb/test_ruby_lex.rb b/test/irb/test_ruby_lex.rb
index e4dea3d662..d9b1418cbe 100644
--- a/test/irb/test_ruby_lex.rb
+++ b/test/irb/test_ruby_lex.rb
@@ -10,14 +10,15 @@ module TestIRB
     Row = Struct.new(:content, :current_line_spaces, :new_line_spaces, :nesting_level)
 
     class MockIO_AutoIndent
-      def initialize(params, &assertion)
+      attr_reader :calculated_indent
+
+      def initialize(*params)
         @params = params
-        @assertion = assertion
+        @calculated_indent
       end
 
       def auto_indent(&block)
-        result = block.call(*@params)
-        @assertion.call(result)
+        @calculated_indent = block.call(*@params)
       end
     end
 
@@ -29,20 +30,56 @@ module TestIRB
       restore_encodings
     end
 
-    def assert_indenting(lines, correct_space_count, add_new_line)
+    def calculate_indenting(lines, add_new_line)
       lines = lines + [""] if add_new_line
       last_line_index = lines.length - 1
       byte_pointer = lines.last.length
 
       context = build_context
       context.auto_indent_mode = true
+
       ruby_lex = RubyLex.new(context)
-      io = MockIO_AutoIndent.new([lines, last_line_index, byte_pointer, add_new_line]) do |auto_indent|
-        error_message = "Calculated the wrong number of spaces for:\n #{lines.join("\n")}"
-        assert_equal(correct_space_count, auto_indent, error_message)
-      end
-      ruby_lex.set_input(io)
+      mock_io = MockIO_AutoIndent.new(lines, last_line_index, byte_pointer, add_new_line)
+
+      ruby_lex.set_input(mock_io)
       ruby_lex.set_auto_indent
+      mock_io.calculated_indent
+    end
+
+    def assert_row_indenting(lines, row)
+      actual_current_line_spaces = calculate_indenting(lines, false)
+
+      error_message = <<~MSG
+        Incorrect spaces calculation for line:
+
+        ```
+      > #{lines.last}
+        ```
+
+        All lines:
+
+        ```
+        #{lines.join("\n")}
+        ```
+      MSG
+      assert_equal(row.current_line_spaces, actual_current_line_spaces, error_message)
+
+      error_message = <<~MSG
+        Incorrect spaces calculation for line after the current line:
+
+        ```
+        #{lines.last}
+      >
+        ```
+
+        All lines:
+
+        ```
+        #{lines.join("\n")}
+        ```
+      MSG
+      actual_next_line_spaces = calculate_indenting(lines, true)
+      assert_equal(row.new_line_spaces, actual_next_line_spaces, error_message)
     end
 
     def assert_nesting_level(lines, expected, local_variables: [])
@@ -108,8 +145,7 @@ module TestIRB
       lines = []
       input_with_correct_indents.each do |row|
         lines << row.content
-        assert_indenting(lines, row.current_line_spaces, false)
-        assert_indenting(lines, row.new_line_spaces, true)
+        assert_row_indenting(lines, row)
       end
     end
 
@@ -124,8 +160,7 @@ module TestIRB
       lines = []
       input_with_correct_indents.each do |row|
         lines << row.content
-        assert_indenting(lines, row.current_line_spaces, false)
-        assert_indenting(lines, row.new_line_spaces, true)
+        assert_row_indenting(lines, row)
       end
     end
 
@@ -143,8 +178,7 @@ module TestIRB
       lines = []
       input_with_correct_indents.each do |row|
         lines << row.content
-        assert_indenting(lines, row.current_line_spaces, false)
-        assert_indenting(lines, row.new_line_spaces, true)
+        assert_row_indenting(lines, row)
       end
     end
 
@@ -157,8 +191,7 @@ module TestIRB
       lines = []
       input_with_correct_indents.each do |row|
         lines << row.content
-        assert_indenting(lines, row.current_line_spaces, false)
-        assert_indenting(lines, row.new_line_spaces, true)
+        assert_row_indenting(lines, row)
       end
     end
 
@@ -177,8 +210,7 @@ module TestIRB
       lines = []
       input_with_correct_indents.each do |row|
         lines << row.content
-        assert_indenting(lines, row.current_line_spaces, false)
-        assert_indenting(lines, row.new_line_spaces, true)
+        assert_row_indenting(lines, row)
       end
     end
 
@@ -253,8 +285,7 @@ module TestIRB
       lines = []
       input_with_correct_indents.each do |row|
         lines << row.content
-        assert_indenting(lines, row.current_line_spaces, false)
-        assert_indenting(lines, row.new_line_spaces, true)
+        assert_row_indenting(lines, row)
       end
     end
 
@@ -266,8 +297,7 @@ module TestIRB
       lines = []
       input_with_correct_indents.each do |row|
         lines << row.content
-        assert_indenting(lines, row.current_line_spaces, false)
-        assert_indenting(lines, row.new_line_spaces, true)
+        assert_row_indenting(lines, row)
       end
     end
 
@@ -279,8 +309,7 @@ module TestIRB
       lines = []
       input_with_correct_indents.each do |row|
         lines << row.content
-        assert_indenting(lines, row.current_line_spaces, false)
-        assert_indenting(lines, row.new_line_spaces, true)
+        assert_row_indenting(lines, row)
       end
     end
 
@@ -292,8 +321,7 @@ module TestIRB
       lines = []
       input_with_correct_indents.each do |row|
         lines << row.content
-        assert_indenting(lines, row.current_line_spaces, false)
-        assert_indenting(lines, row.new_line_spaces, true)
+        assert_row_indenting(lines, row)
       end
     end
 
@@ -319,8 +347,7 @@ module TestIRB
       lines = []
       input_with_correct_indents.each do |row|
         lines << row.content
-        assert_indenting(lines, row.current_line_spaces, false)
-        assert_indenting(lines, row.new_line_spaces, true)
+        assert_row_indenting(lines, row)
       end
     end
 
@@ -350,8 +377,7 @@ module TestIRB
       lines = []
       input_with_correct_indents.each do |row|
         lines << row.content
-        assert_indenting(lines, row.current_line_spaces, false)
-        assert_indenting(lines, row.new_line_spaces, true)
+        assert_row_indenting(lines, row)
       end
     end
 
@@ -366,8 +392,7 @@ module TestIRB
       lines = []
       input_with_correct_indents.each do |row|
         lines << row.content
-        assert_indenting(lines, row.current_line_spaces, false)
-        assert_indenting(lines, row.new_line_spaces, true)
+        assert_row_indenting(lines, row)
         assert_nesting_level(lines, row.nesting_level)
       end
     end
@@ -387,8 +412,7 @@ module TestIRB
       lines = []
       input_with_correct_indents.each do |row|
         lines << row.content
-        assert_indenting(lines, row.current_line_spaces, false)
-        assert_indenting(lines, row.new_line_spaces, true)
+        assert_row_indenting(lines, row)
         assert_nesting_level(lines, row.nesting_level)
       end
     end
@@ -436,8 +460,7 @@ module TestIRB
       lines = []
       input_with_correct_indents.each do |row|
         lines << row.content
-        assert_indenting(lines, row.current_line_spaces, false)
-        assert_indenting(lines, row.new_line_spaces, true)
+        assert_row_indenting(lines, row)
         assert_nesting_level(lines, row.nesting_level)
       end
     end
@@ -452,8 +475,7 @@ module TestIRB
       lines = []
       input_with_correct_indents.each do |row|
         lines << row.content
-        assert_indenting(lines, row.current_line_spaces, false)
-        assert_indenting(lines, row.new_line_spaces, true)
+        assert_row_indenting(lines, row)
         assert_nesting_level(lines, row.nesting_level)
       end
     end
@@ -468,8 +490,7 @@ module TestIRB
       lines = []
       input_with_correct_indents.each do |row|
         lines << row.content
-        assert_indenting(lines, row.current_line_spaces, false)
-        assert_indenting(lines, row.new_line_spaces, true)
+        assert_row_indenting(lines, row)
         assert_nesting_level(lines, row.nesting_level)
       end
     end
@@ -485,8 +506,7 @@ module TestIRB
       lines = []
       input_with_correct_indents.each do |row|
         lines << row.content
-        assert_indenting(lines, row.current_line_spaces, false)
-        assert_indenting(lines, row.new_line_spaces, true)
+        assert_row_indenting(lines, row)
         assert_nesting_level(lines, row.nesting_level)
       end
     end
@@ -501,8 +521,7 @@ module TestIRB
       lines = []
       input_with_correct_indents.each do |row|
         lines << row.content
-        assert_indenting(lines, row.current_line_spaces, false)
-        assert_indenting(lines, row.new_line_spaces, true)
+        assert_row_indenting(lines, row)
         assert_nesting_level(lines, row.nesting_level)
       end
     end
@@ -517,8 +536,7 @@ module TestIRB
       lines = []
       input_with_correct_indents.each do |row|
         lines << row.content
-        assert_indenting(lines, row.current_line_spaces, false)
-        assert_indenting(lines, row.new_line_spaces, true)
+        assert_row_indenting(lines, row)
         assert_nesting_level(lines, row.nesting_level)
       end
     end
@@ -533,8 +551,7 @@ module TestIRB
       lines = []
       input_with_correct_indents.each do |row|
         lines << row.content
-        assert_indenting(lines, row.current_line_spaces, false)
-        assert_indenting(lines, row.new_line_spaces, true)
+        assert_row_indenting(lines, row)
         assert_nesting_level(lines, row.nesting_level)
       end
     end
@@ -549,8 +566,7 @@ module TestIRB
       lines = []
       input_with_correct_indents.each do |row|
         lines << row.content
-        assert_indenting(lines, row.current_line_spaces, false)
-        assert_indenting(lines, row.new_line_spaces, true)
+        assert_row_indenting(lines, row)
         assert_nesting_level(lines, row.nesting_level)
       end
     end
@@ -575,8 +591,7 @@ module TestIRB
       lines = []
       input_with_correct_indents.each do |row|
         lines << row.content
-        assert_indenting(lines, row.current_line_spaces, false)
-        assert_indenting(lines, row.new_line_spaces, true)
+        assert_row_indenting(lines, row)
         assert_nesting_level(lines, row.nesting_level)
       end
     end
@@ -592,8 +607,7 @@ module TestIRB
       lines = []
       input_with_correct_indents.each do |row|
         lines << row.content
-        assert_indenting(lines, row.current_line_spaces, false)
-        assert_indenting(lines, row.new_line_spaces, true)
+        assert_row_indenting(lines, row)
         assert_nesting_level(lines, row.nesting_level)
       end
     end
@@ -611,8 +625,7 @@ module TestIRB
       lines = []
       input_with_correct_indents.each do |row|
         lines << row.content
-        assert_indenting(lines, row.current_line_spaces, false)
-        assert_indenting(lines, row.new_line_spaces, true)
+        assert_row_indenting(lines, row)
         assert_nesting_level(lines, row.nesting_level)
       end
     end