What counts as an external function call?

Question

I am trying to figure out what counts as an external function call.

Let's say Contract X calls function A in a third-party non-related Contract B and then that function turns around and calls function B in its own (Contract X) contract...is that considered an external function call because it originated from outside or is it considered an internal function call because it called a function within itself?

For some extra context, I am looking at this function...it is called by a third party but then calls a bunch of functions in itself. It uses try/catch which is supposed to only be for external function calls and contract creation

function performUpkeep() public nonReentrant
        {
        // Perform the multiple steps of performUpkeep()
        try this.step1() {}
        catch (bytes memory error) { emit UpkeepError("Step 1", error); }

        try this.step2(msg.sender) {}
        catch (bytes memory error) { emit UpkeepError("Step 2", error); }

        try this.step3() {}
        catch (bytes memory error) { emit UpkeepError("Step 3", error); }

        try this.step4() {}
        catch (bytes memory error) { emit UpkeepError("Step 4", error); }

        try this.step5() {}
        catch (bytes memory error) { emit UpkeepError("Step 5", error); }

        try this.step6() {}
        catch (bytes memory error) { emit UpkeepError("Step 6", error); }

        try this.step7() {}
        catch (bytes memory error) { emit UpkeepError("Step 7", error); }

        try this.step8() {}
        catch (bytes memory error) { emit UpkeepError("Step 8", error); }

        try this.step9() {}
        catch (bytes memory error) { emit UpkeepError("Step 9", error); }

        try this.step10() {}
        catch (bytes memory error) { emit UpkeepError("Step 10", error); }

        try this.step11() {}
        catch (bytes memory error) { emit UpkeepError("Step 11", error); }
        }

Answer 1

The syntax makes those external. by doing this.yourFunction() instead of simply yourFunction(), you're effectively making an external call to yourself (it's a CALL opcode, not a JUMP or a JUMPI, you can call public or external function that way, but not internal ones, msg.sender and msg.value are updated and you can do try{...} catch).

Note that there must be a reason why this is done like that, if your issue is just that you need to test if a function succeeded it's always gonna be cheaper to create logic yourself to handle that than making external calls, so there must be something else than just "the dev needed a way to catch errors".