Don't expect every pattern in a route to have the specified stop with constrained transfers

[optionsome]

Summary

Adds validation for indexing constrained transfers so that it can handle situations where a route doesn't have a stop specified in a transfer in every pattern.

Issue

closes #3867

Unit tests

Should they be added?

Code style

Have you followed the suggested code style?
Yes

Documentation

not needed

Changelog

From title

[optionsome]

I'm not sure if I like the way I've fixed this issue. However, this was the easiest way to fix it but I'm more than happy to change it to something else. Below are some alternative ways to do it:

• Validate that the stop exists in the pattern before fetching its index
• Return -1 as index if it doesn't exist on the pattern and check that it's not -1 before adding the transfer point. This would either require to change the existing uses of the function that currently throws the exception or implement another version of it that doesn't throw an exception-
• Change the exception to be less generic

[leonardehrenfried]

I would also prefer a solution that doesn't use exceptions as a control flow statements.

Is this due to invalid input data or is this a legal state that we have to take into account when building the index?

[optionsome]

This is a legal state and it's even expected to happen quite often so logging when it happens doesn't really make sense

[optionsome]

I rewrote it by returning -1 when stop is not on pattern. Should I add tests for this somewhere?

[leonardehrenfried]

Wasn't there any calling code that needed to be updated?

[optionsome]

Wasn't there any calling code that needed to be updated?

Didn't seem like so. Most places called different method for finding stop index in the stop pattern.