commit daed00e76b6cd4a97a10c95df4ba6750e37ba1bf
author Steven Grady <slgrady@google.com> Fri Dec 20 13:58:00 2024 -0800
committer CQ Bot <fuchsia-internal-scoped@luci-project-accounts.iam.gserviceaccount.com> Fri Dec 20 13:58:00 2024 -0800
tree 90db8866b3b4cda68b18ebf5680565cf61f3e68b
parent 99289f071c3968d3d3fca59783ef09fdda7dd956

[ffx] Fix strict handling of env vars in config

When in strict mode, we need to reject env vars. But rather than
just not doing the env_var mapping, which would leave the strings
as "$ENV_VAR" which is never what we want. It would cause problems
like failing to find separately-built tools, or failing to find
the SDK path, without providing a useful error message.

Instead, we should actionable error to the user, reporting the
name of the config variable that failed, and show them the string
that failed to be map.

This requires some surgery to config: e.g. getting away from the type
magic involved in TryFrom (and its associated error type). Instead,
there is now a TryConvert trait which always returns ConfigError.
There is also a new member of the ConfigError enum, BadValue, which
is only returned (currently) when in strict mode. It contains a useful
description of why the conversion failed.

This error was introduced because it can carry information about why
the failure occurred, but it also lets a caller determine whether they
care whether it failed. In some cases (e.g. in get_target_specifier())
we can just ignore it and assume the value is None. There is now a
convenience function, get_optional(), which the caller can use when
it doesn't care about this particular error.

Fixed: 383636241
Fixed: 382333204
Change-Id: Ica197d41f92d44d96b40c898795b4b7d20bcb758
Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/1177196
Commit-Queue: Steven Grady <slgrady@google.com>
Reviewed-by: Colin Nelson <colnnelson@google.com>