Change bin/prism errors to take source and print errors

This is more akin to how all the other ones work.
Instead I added most of this to the errors test like focusing
a few specifically and creating new expectations.

Author: Earlopain

bin/prism

@@ -161,36 +161,17 @@ module Prism
       unicode_lists(found) if found == Encoding::UTF_8 || found == Encoding::UTF8_MAC
     end
 
-    # bin/prism error [name] [source]
+    # bin/prism error [source]
     def error(argv)
-      name = argv.shift
-
-      source = nil
-      filepath = File.expand_path("../test/prism/errors/#{name}.txt", __dir__)
+      source, filepath = read_source(argv)
+      result = Prism.parse(source)
 
-      if argv.empty?
-        raise "Expected #{filepath} to exist" unless File.file?(filepath)
 
-        source = File.read(filepath, binmode: true, external_encoding: Encoding::UTF_8)
-        source = source.lines.grep_v(/^\s*\^/).join.gsub(/\n*\z/, "")
+      if result.errors.any?
+        puts result.errors_format
       else
-        if File.file?(filepath)
-          counter = 1
-
-          begin
-            current = "#{File.dirname(filepath)}/#{File.basename(filepath, ".txt")}_#{counter += 1}.txt"
-          end while File.file?(current)
-
-          filepath = current
-        end
-
-        source, _ = read_source(argv)
+        puts "No syntax errors for #{filepath}"
       end
-
-      result = Prism.parse(source)
-      raise "Expected #{source.inspect} to have errors" if result.success?
-
-      File.write(filepath, result.errors_format)
     end
 
     # bin/prism lex [source]

test/prism/errors_test.rb

@@ -7,7 +7,7 @@
 module Prism
   class ErrorsTest < TestCase
     base = File.expand_path("errors", __dir__)
-    filepaths = Dir["**/*.txt", base: base]
+    filepaths = Dir[ENV.fetch("FOCUS", "**/*.txt"), base: base]
 
     filepaths.each do |filepath|
       ruby_versions_for(filepath).each do |version|
@@ -100,6 +100,10 @@ def assert_errors(filepath, version)
       refute_empty errors, "Expected errors in #{filepath}"
 
       actual = result.errors_format
+      if expected != actual && ENV["UPDATE_SNAPSHOTS"]
+        File.write(filepath, actual)
+      end
+
       assert_equal expected, actual, "Expected errors to match for #{filepath}"
     end
   end