No junction box on exterior light?

To my understanding this is 1000% not ok by any codes. (Disclaimer, I'm an electrical engineer, not an electrician)

So far as I know, all wire junctions need to be completely enclosed in a non-flammable box. This clearly is not.

There is no electrical shock hazard here. It's a fire hazard. If the flammability spec of your wall is known, MAYBE this is OK but a general contractor is not in a position to make that call --- It would have to be made by a licensed PE (professional engineer).

https://www.prospertx.gov/wp-content/uploads/NFPA-NEC-Guide-to-Wire-Box-Installation-01-10-17.pdf

314.19 Boxes Enclosing Flush Devices. Boxes used to enclose flush devices shall be of such design that the devices will be completely enclosed on back and sides and substantial support for the devices will be provided. Screws for supporting the box shall not be used in attachment of the device contained therein.

Your local building inspector may have a difference of opinion and think this is OK. Of course, if you contact him/her, you might be opening Pandoras box.

In reality, the risk is pretty small. Maybe 1:1,000,000 odds of an issue. But the codes are written with the expectation there will be a million installations and NONE should cause somebody to die.

Lots of fixtures or canopies are made to attach directly to cable or conduit, with integral cable clamps or knockouts for suitable (listed, rated...) cable clamps or conduit entry. This one is not.

The NEC requires light fixtures be listed, and used as intended by the manufacturer. The metal ring in your photo is not for direct surface mounting, it's made to go on a box, using it for a surface mount is not compliant.

There are a few other code provisions that could be problematic, protection from abrasion and water seepage, etc. They didn't even wrap the ground wire around the screw. But the main thing you need here is a box. Retrofitting it will be a bit of a project.

The box doesn't necessarily fix everything; the fixture must be suitable (listed, rated for outdoor use, etc.) and made to mount on the type of box that you install.

Should be ok running the wire like that, but not the connection. You could install a shallow "pancake" electrical box on the wall and then the wire would be within the box. (e.g. https://www.lowes.com/pd/RACO-1-Gang-Gray-Metal-New-Work-Shallow-Ceiling-Pans-Ceiling-Electrical-Box/1099827)