Throw better exception message for client eval

[ajcvickers]

Fixes #16133 and also partial fix for #15937

This is far from perfect and needs some further work. For example, see #17236

No issues reference #14935 any more; new issues cover things not fixed here but which were refeceing that issue.

[roji]

LGTM.

There seem to be some cases where tests for something that is currently untranslatable have been changed to assert on translation failure - it seems better to keep them skipped (and ideally reference an issue).

[roji]

Could be translated? Also other random-exercising tests below

[ajcvickers]

Likewise

[smitpatel]

Not possible to translate for all providers. We should revisit in future, how do we provide tests which are totally conditionally in provider. No suitable relational available. (or throwing can be relational translation)

---

In reply to: 315191515 [](ancestors = 315191515)

[roji]

Should be translatable (in the future)?

[ajcvickers]

Likewise

[smitpatel]

Translatable. I think @ajcvickers is already working on issue.

---

In reply to: 315192777 [](ancestors = 315192777)

[smitpatel]

• Use null returning and base throwing would simplify code & also allow to print better message.
• Every exception in query should not be printed as translation failed. Translation failure should only be printed when we fail to translate. We should discuss this.
• I did not look at all the tests, but are all tests which are not throwing exception right now which were disabled with client eval in past are enabled in this PR?

Requires follow-up discussion

[smitpatel]

Unable to process Expression in visitor. + thing about using AsEnumerable etc.

[ajcvickers]

Going to merge this now, then work on the feedback in a separate PR.

[ajcvickers]

@smitpatel @divega Messages for the two general cases:

The LINQ expression '{expression}' could not be translated. Either rewrite the query in a form that can be translated, or switch to client evaluation explicitly, for example by by inserting a call to either AsEnumerable(), AsAsyncEnumerable(), ToList(), or ToListAsync(), if this is appropriate. See https://go.microsoft.com/fwlink/?linkid=2101038 for more detailed information.

Processing of the LINQ expression '{expression}' failed. This may indicate either a bug or a limitation in EF Core. See https://go.microsoft.com/fwlink/?linkid=2101038 for more detailed information.

With two different fwlinks?

Thoughts?

[smitpatel]

Also include visitor name in 2nd exception message. LGTM otherwise.

[smitpatel]

We need to improve this printing. cc: @maumar

[smitpatel]

@roji - I commented on all the why not translated comments. If you see any other test which you think we should translate then, please file an issue with the test name and what should be the translation.

[divega]

The new fwlink for the "processing the linq expression failed" case is https://go.microsoft.com/fwlink/?linkid=2101433.

[roji]

@smitpatel realistically we should probably just do a pass later and search for translation failure assertions in tests, I don't think there's anything urgent in there for 3.0 (at least not that I can tell).

[smitpatel]

Nothing urgent. I meant to say whenever you decide to do pass or see something out of place. That is true even without regards of client eval changes.