Refactor ColumnDumper to support consistent Virtual column with Rails

[yahonda]

This pull request addresses these 3 failures:

$ ARCONN=oracle bundle exec ruby -w -Itest test/cases/schema_dumper_test.rb -n /no_line_up/

... snip ...

Finished in 21.899343s, 0.0913 runs/s, 0.5480 assertions/s.

  1) Failure:
SchemaDumperTest#test_arguments_no_line_up [test/cases/schema_dumper_test.rb:100]:
Failed assertion, no message given.


  2) Failure:
SchemaDumperTest#test_types_no_line_up [test/cases/schema_dumper_test.rb:94]:
Failed assertion, no message given.

2 runs, 12 assertions, 2 failures, 0 errors, 0 skips

$ ARCONN=oracle bundle exec ruby -w -Itest test/cases/migration_test.rb -n test_deprecate_migration_keys

... snip ...



# Running:

F

Finished in 0.005173s, 193.2977 runs/s, 193.2977 assertions/s.

  1) Failure:
CopyMigrationsTest#test_deprecate_migration_keys [test/cases/migration_test.rb:1143]:
Expected a deprecation warning within the block but received none

1 runs, 1 assertions, 1 failures, 0 errors, 0 skips
$

Refer these changes at Rails:

• Extract format_colspec to format column spec rails/rails#26756
• Add Generated Columns support for MySQL 5.7 rails/rails#22589
• rails/rails@df84e986721
• Deprecate ColumnDumper#migration_keys rails/rails#27884

This commit introduces Virtual column schema dumper format change. :type attribute shown next to column name.

Align changes has been introduced by rails/rails@df84e986721 .

• Before this commit:

ActiveRecord::Schema.define(version: 0) do

  create_table "test_names", force: :cascade do |t|
    t.string  "first_name"
    t.string  "last_name"
    t.virtual "full_name",                limit: 512,                as: "\"FIRST_NAME\"||', '||\"LAST_NAME\"",                              type: :string
    t.virtual "short_name",               limit: 300,                as: "COALESCE(\"FIRST_NAME\",\"LAST_NAME\")",                           type: :string
    t.virtual "abbrev_name",              limit: 100,                as: "SUBSTR(\"FIRST_NAME\",1,50)||' '||SUBSTR(\"LAST_NAME\",1,1)||'.'", type: :string
    t.virtual "name_ratio",                                          as: "LENGTH(\"FIRST_NAME\")*10/LENGTH(\"LAST_NAME\")*10"
    t.virtual "full_name_length",                     precision: 38, as: "LENGTH(\"FIRST_NAME\"||', '||\"LAST_NAME\")",                      type: :integer
    t.virtual "field_with_leading_space", limit: 300,                as: "' '||\"FIRST_NAME\"||' '",                                         type: :string
  end

end

• After this commit:

ActiveRecord::Schema.define(version: 0) do

  create_table "test_names", force: :cascade do |t|
    t.string "first_name"
    t.string "last_name"
    t.virtual "full_name", type: :string, limit: 512, as: "\"FIRST_NAME\"||', '||\"LAST_NAME\""
    t.virtual "short_name", type: :string, limit: 300, as: "COALESCE(\"FIRST_NAME\",\"LAST_NAME\")"
    t.virtual "abbrev_name", type: :string, limit: 100, as: "SUBSTR(\"FIRST_NAME\",1,50)||' '||SUBSTR(\"LAST_NAME\",1,1)||'.'"
    t.virtual "name_ratio", as: "LENGTH(\"FIRST_NAME\")*10/LENGTH(\"LAST_NAME\")*10"
    t.virtual "full_name_length", type: :integer, precision: 38, as: "LENGTH(\"FIRST_NAME\"||', '||\"LAST_NAME\")"
    t.virtual "field_with_leading_space", type: :string, limit: 300, as: "' '||\"FIRST_NAME\"||' '"
  end

end