fix(otlptrace,otlpmetric): remove endpoint URL path cleaning

[mjq]

When setting an explicit OTLP traces endpoint URL (via otlptracehttp.WithEndpointURL or the OTEL_EXPORTER_OTLP_TRACES_ENDPOINT environment variable), any given trailing slash is stripped. This makes it impossible to export traces to an endpoint requiring a trailing slash. It also conflicts with the spec:

For the per-signal variables (OTEL_EXPORTER_OTLP_<signal>_ENDPOINT), the URL MUST be used as-is without any modification. The only exception is that if an URL contains no path part, the root path / MUST be used (see Example 2).

This stripping happens due to the use of path.Clean in otlpconfig.cleanPath. From the path.Clean docs:

The returned path ends in a slash only if it is the root "/".

Other signals appear to use path.Clean and might therefore have the same bug, but I've only tested and fixed traces.

Fixes #6709.

[dmathieu]

the URL MUST be used as-is without any modification

This kind of indicates we should remove path.Clean entirely.

[pellared]

@mjq, ping 😉

See: #6710 (comment)

[mjq]

@pellared Sorry for the delay! I incorporated @dmathieu's feedback re: removing the usage of path.Clean. I removed it from the equivalent config option in metrics as well for consistency.

I also realized I was changing generated files in the original commit - now the changes are made to the templates and applied with make generate.

[pellared]

What about otlplog?

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 82.3%. Comparing base (274e939) to head (7c0d68a).
Report is 1 commits behind head on main.

Additional details and impacted files

@@          Coverage Diff          @@
##            main   #6710   +/-   ##
=====================================
  Coverage   82.3%   82.3%           
=====================================
  Files        263     263           
  Lines      24421   24421           
=====================================
+ Hits       20099   20102    +3     
+ Misses      3940    3937    -3     
  Partials     382     382           

Files with missing lines	Coverage Δ
...tlpmetric/otlpmetricgrpc/internal/oconf/options.go	89.0% <100.0%> (ø)
...tlpmetric/otlpmetrichttp/internal/oconf/options.go	91.9% <100.0%> (ø)
...trace/otlptracegrpc/internal/otlpconfig/options.go	94.3% <100.0%> (ø)
...trace/otlptracehttp/internal/otlpconfig/options.go	91.1% <100.0%> (ø)

... and 2 files with indirect coverage changes

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[mjq]

I fixed the failing changelog check (bad automatic merge with main).

What about otlplog?

@pellared With this change path.Clean no longer appears in the codebase, and from poking around I couldn't find any equivalent code for log configs.

[pellared]

I fixed the failing changelog check (bad automatic merge with main).

What about otlplog?

@pellared With this change path.Clean no longer appears in the codebase, and from poking around I couldn't find any equivalent code for log configs.

Thanks. I noticed that otlplog does not even do strings.TrimSpace which is probably OK 😉

[mjq]

@pellared @dmathieu I don't have permission to merge this, so please go ahead if everything looks good or let me know if there are any further changes I should make 👍 Thanks!

[pellared]

@mjq, thank you very much for your contribution.