Bug: invalid regex in extend-ignore-identifiers-re silently stops config file parsing

[phip1611]

I found an error in the typos utility, I think. It seems that as soon as one entry in extend-ignore-identifiers-re is invalid

[default]
extend-ignore-identifiers-re = [
  # This entry causes harm; it should be "foo\\(" but no error is reported
  "foo(",
]

the parsing silently fails and causes that all other configurations, such as [default.extend-identifiers] and [default.extend-words] are silently ignored. That's very unfortunate.

One can verify this following these steps:

• create a .typos.toml with the following content:

  [default]
  extend-ignore-identifiers-re = [
    # This entry causes harm; it should be "foo\\(" but no error is reported
    "foo("
  ]
  
  [default.extend-identifiers]
  bar = "foo"
  
  [default.extend-words]
  bar = "foo"

• run typos --config .typos.toml --dump-config - | grep 'foo'
• error you see no results
• remove the foo( in the config
• run typos --config .typos.toml --dump-config - | grep 'foo'
• it works

Expected Behaviour:

Typos should tell which regex is invalid and why it is invalid, instead of silently dropping that error. Furthermore, it should continue parsing the config file.

[epage]

My guess as to what is happening is that serde_derive when it sees any error in a flatten of an Option, it uses None rather than being able to distinguish what are recoverable or critical errors.