Redmine

To not just ask for features to be added or changed, but rather provide some input myself, let me add the following suggestion for an implementation to discuss.
Maybe someone with more advanced Redmine knowledge then myself could have a look whether this is feasible and would stand a chance to be added into the Redmine codebase.
I might then be able to provide a patch.

Based on Github Commit 506fc9d74cdb67af2eaea27662420ec07e32b2f3 or Redmine SVN R21238 I have identified the following code to be related to how start-date and due-date in parent issues are handled:

/app/models/issue.rb:L1411

  def dates_derived?
    !leaf? && Setting.parent_issue_dates == 'derived'
  end

which defines dates_derived, for all issues with child-issues, if the corresponding configuration option is set.

/app/models/issue.rb:L529

    if dates_derived?
      names -= %w(start_date due_date)
    end

which removes start-date and due-date from the available/editable fields.

/app/models/issue.rb:L1823

      if p.dates_derived?
        # start/due dates = lowest/highest dates of children
        p.start_date = p.children.minimum(:start_date)
        p.due_date = p.children.maximum(:due_date)
        if p.start_date && p.due_date && p.due_date < p.start_date
          p.start_date, p.due_date = p.due_date, p.start_date
        end
      end

which controls how the field values are calculated if the config option is set to "derived".

app/helpers/settings_helper.rb:L185

  def parent_issue_dates_options
    options = [
      [:label_parent_task_attributes_derived, 'derived'],
      [:label_parent_task_attributes_independent, 'independent']
    ]

which defines the available configuration options for how dates are handled.

I would now suggest adding another option "partially derived" to

app/helpers/settings_helper.rb

  def parent_issue_dates_options
    options = [
      [:label_parent_task_attributes_derived, 'derived'],
      [:label_parent_task_attributes_partially_derived, 'partially_derived'],
      [:label_parent_task_attributes_independent, 'independent']
    ]

as well as a definition of "dates_partially_derived" to

/app/models/issue.rb

  def dates_partially_derived?
    !leaf? && Setting.parent_issue_dates == 'partially_derived'
  end

and a new calculation method (not tested yet, consider as pseudo code) for the partially derived case to

/app/models/issue.rb:

      if p.dates_partially_derived?
        # start/due dates = lowest/highest dates of children or own date
        p.start_date = [p.children.minimum(:start_date), p.start_date].compact.min
        p.due_date = [p.children.maximum(:due_date), p.due_date].compact.max
        if p.start_date && p.due_date && p.due_date < p.start_date
          p.start_date, p.due_date = p.due_date, p.start_date
        end
      end

The same partial options could also be added to parent_issue_priority_options and parent_issue_done_ratio_options.
This would result in the following overall behaviour when the partial options are selected.

• Start-date can not be later than first child start date, but can be sooner
• Due-date can not be sooner than last child end date, but can be later
• Done ratio can not be higher than combined children's done ration, but can be lower
• Priority can not be lower than maximum child priority, but can be higher

However, at first, I would only consider handling the dates, leaving done-ratio and priority for later.

Of course there is more to this, like localization e.g. in config/locales/en-GB.yml or config/locales/de.yml, I would suggest the following:

config/locales/en-GB.yml

label_parent_task_attributes_derived: Calculated from subtasks
label_parent_task_attributes_partially_derived: Partially calculated from subtasks
label_parent_task_attributes_independent: Independent of subtasks

config/locales/de.yml

label_parent_task_attributes_derived: Abgeleitet von untergeordneten Tickets
label_parent_task_attributes_partially_derived: Teilweise abgeleitet von untergeordneten Tickets
label_parent_task_attributes_independent: Unabhängig von untergeordneten Tickets

Another topic are the test cases in /test/unit/issue_subtasking_test.rb

• test_parent_dates_should_be_read_only_with_parent_issue_dates_set_to_derived
• test_parent_dates_should_be_lowest_start_and_highest_due_dates_with_parent_issue_dates_set_to_derived
• test_reschuling_a_parent_should_reschedule_subtasks_with_parent_issue_dates_set_to_derived
• test_parent_dates_should_be_editable_with_parent_issue_dates_set_to_independent
• test_parent_dates_should_not_be_updated_with_parent_issue_dates_set_to_independent
• test_reschuling_a_parent_should_not_reschedule_subtasks_with_parent_issue_dates_set_to_independent

• test_parent_dates_should_be_editable_with_parent_issue_dates_set_to_partially_derived
• test_parent_dates_should_be_lowest_start_and_highest_due_dates_with_parent_issue_dates_set_to_partially_derived

I am not yet sure about the rescheduling part, which possibly means my suggestion above might also be incomplete.

As stated above, suggestions and hints are welcome. In the meantime I will be working on getting this to run.

I've added unit test for all new functionality as well as fixed a bug that showed itself during testing.
The test are added to the file "test/unit/issue_subtasking_test.rb" which I ran using ruby test/unit/issue_substasking.rb as well as via the full test run using rake test.

rake test summary said:
4995 runs, 21332 assertions, 3 failures, 1 error, 6 skips.

The problematic tests are as follows:

• Failure 1: "I18nTest#test_locales_validness" and
• Failure 2: "I18nTest:test_language_options" from test/unit/lib/redmine/i18n_test.rb, both with "Expected 50, Actual 49".

I am still looking into this. It might be related to the above mentioned (#34609-5):

However for some reason rake locales:update did not copy all five new strings from en.yml [...].

The locale configurations for en, en-GB and de contain all five new entries

1. en:activerecord:errors:messages:earlier_than_maximum_due_date (Line 133)
2. en:activerecord:errors:messages:later_than_minimum_start_date (Line 134)
3. en:activerecord:errors:messages:priority_lower_than_children (Line 135)
4. en:activerecord:errors:messages:done_ratio_higher_than_children (Line 136)
5. en:label_parent_task_attributes_partially_derived (Line 1070)

rake locales:update transfers only the last new entry to all other locale files.

EDIT: According to its description locales:update is not able to update the first four entries, as they are not top-level. These would need to be added manually or locale:update would need to be expanded to handle added non-top-level keys.

On the other hand running these tests via ruby test/unit/lib/redmine/i18n_test.rb on the current origin/master, without my changes results in the same failure. So it might not be related to my changes at all.

• Failure 3: "AttachmentControllerTest#test_thumbnail_for_pdf_should_be_png" and
• Error 1: AttachmentTest#test_thumbnail_should_generate_the_thumbnail" from "test/unit/attachement_test.rb"

These two seem unrelated, something about a security policy.

Attached the patch (patch34609-3.diff) including all changes against the now current Git 7b9f5af and SVN R21268.

I would consider it ready for a review.

Somewhat off topic: As part of my effort to this patch I will provide up-to-date documentation on how to set up a Redmine development system on Debian 11, which might be a useful addition to the Developer_Guide or rather a subpage of it.