Print full error chain when failing to load grammar

[NiklasJonsson]

As per the documentation in anyhow: https://docs.rs/anyhow/latest/anyhow/struct.Error.html#display-representations to print the full error, one should use {:#}.

This helped me debug an error where a .so file would fail to load for a treesitter grammar by giving more information on the error so I'd figured I'd open a PR so that it might help others.

I didn't write a test because I'm not very familiar with the helix code and test structure but if you'd like one, please give some suggestion on how to implement it and I will 😄

[drybalka]

I don't think a test is needed, as your PR only changes the error display. It would be helpful, however, if you could provide a recipe for testing it manually, so that I can compare the errors. In other words, what do I need to do to break the treesitter grammar loading and get an error from this part of code?

[NiklasJonsson]

Sure, here is an example:

1. Create a cpp file main.cpp

   int main() {
     return 1;
   }

2. Open it and verify that the syntax highlighting works.
3. Rename the cpp grammar file. mv <helix-runtime-dir>/grammars/cpp.dll <helix-runtime-dir>/grammars/cpp2.dll (I'm on windows right now, should be .so on linux)
4. Open main.cpp again. Syntax highlighting should not work.
5. Check the logs with :log-open

   helix_core::syntax [ERROR] Failed to load tree-sitter parser for language "cpp": Error opening dynamic library "<helix-runtime-dir>\\grammars\\cpp.dll"
   

But with my change, the logs contain

helix_core::syntax [ERROR] Failed to load tree-sitter parser for language "cpp": Error opening dynamic library "<helix-runtime-dir>\\grammars\\cpp.dll": LoadLibraryExW failed: The specified module could not be found. (os error 126)

The real issue that prompted this PR was that I had built the cpp.so against one libc but at runtime it tried to link against a much older one and got missing symbol errors. I don't have the logs for this though but the above should show the improvement.