[FIX] sale_fixed_discount: fix fixed discount on API-created order lines

[sefirosweb]

This fix when you want to create order via API and you want use discount_fixed instead "discount" rate

Without that the sales_order_line is created with discount_fixed but discount is 0

[rousseldenis]

@sefirosweb Could you fix this?

Moreover, adding a test case for that flow should be great.

[sefirosweb]

@rousseldenis I saw a bit bug when is creating the records i fixed them

[rousseldenis]

/ocabot rebase

[OCA-git-bot]

Congratulations, PR rebased to 16.0.

[rousseldenis]

@sefirosweb Could you improve your commits messages like [IMP] sale_fixed_discount: (...) and fix pre-commit ?

[rousseldenis]

@sefirosweb Do you plan to finish this ?

[sefirosweb]

OK!

[alexey-pelykh]

Thanks for the fix @sefirosweb, the core idea of overriding _compute_discount is the right approach here.

A few things still need attention before this can be merged:

1. Remove _onchange_discount_fixed -- as @rousseldenis mentioned in the earlier inline comment, once _compute_discount is in place the onchange is redundant. The compute method fires in both UI and API contexts, so the onchange should be dropped entirely.

2. Test indentation -- the body of test_05_discount_fixed_when_created_by_api is indented with 12 spaces instead of the expected 8 (4 for class + 4 for method). Please align with the rest of the test file.

3. Missing newline at end of file -- the test file is missing a trailing newline, which will also trip pre-commit.

4. Reuse existing fixtures -- the new test creates its own res.partner and product.product when self.partner and self.product (or self.product2) from setUpClass could be reused. Keeps tests consistent and leaner.

5. Commit messages -- @rousseldenis already flagged this: commits should follow OCA format, e.g. [FIX] sale_fixed_discount: .... The intermediate commits should be squashed into a single clean commit.

Points 1-4 are likely what's causing the CI failures. Should be straightforward to fix up.

[rousseldenis]

Thanks for the fix @sefirosweb, the core idea of overriding _compute_discount is the right approach here.

A few things still need attention before this can be merged:

1. Remove _onchange_discount_fixed -- as @rousseldenis mentioned in the earlier inline comment, once _compute_discount is in place the onchange is redundant. The compute method fires in both UI and API contexts, so the onchange should be dropped entirely.
2. Test indentation -- the body of test_05_discount_fixed_when_created_by_api is indented with 12 spaces instead of the expected 8 (4 for class + 4 for method). Please align with the rest of the test file.
3. Missing newline at end of file -- the test file is missing a trailing newline, which will also trip pre-commit.
4. Reuse existing fixtures -- the new test creates its own res.partner and product.product when self.partner and self.product (or self.product2) from setUpClass could be reused. Keeps tests consistent and leaner.
5. Commit messages -- @rousseldenis already flagged this: commits should follow OCA format, e.g. [FIX] sale_fixed_discount: .... The intermediate commits should be squashed into a single clean commit.

Points 1-4 are likely what's causing the CI failures. Should be straightforward to fix up.

@alexey-pelykh Comments for specific changes should be done in PR's code line level. Please avoid such reviews. Thanks