[tantivy] Fix for schema deserialization error

[ppodolsky]

There is a feature in serde_yaml that it cannot deal with borrowed strings. It makes impossible to deserialize yaml to Schema due to error invalid type: string \"field_name\", expected a borrowed string
This extra allocation is a tol-tol solution, but it's a far more easier way then rewriting whole serde_yaml and I hope deserializing schema is not a hot path.

[fulmicoton]

I don't understand anything about this bug.

Tantivy does not use Yaml. If you really need yaml serialization that's a feature request you want and you will need to explain why this is useful to you.

[ppodolsky]

There was a one line test in the PR that did not work:
serde_yaml::from_str::<FieldEntry>(field_content).unwrap();
or similar
serde_yaml::from_str::<Schema>(schema_content).unwrap();

If you really need yaml serialization that's a feature request

You already have yaml serialization due to using serde crate :) There is just a small trouble with deserialization.

[ppodolsky]

About the reasons - we are storing schemas in files, not in the code. Yaml is much easier for human to read and edit:

[{
  "name": "title",
  "type": "text",
  "options": {
    "indexing": {
      "record": "position",
      "tokenizer": "default"
    },
    "stored": false
  }
}, {
  "name": "body",
  "type": "text",
  "options": {
    "indexing": {
      "record": "position",
      "tokenizer": "default"
    },
    "stored": false
}]

vs

- name: text
  type: text
  options:
    indexing:
      record: position
      tokenizer: default
    stored: true
- name: body
  type: text
  options:
    indexing:
      record: position
      tokenizer: default
    stored: true

You can easily be mistaken with these curvy brackets while editing file manually

[fulmicoton]

I see... And I had missed the fact that the dependency was just a dev-dependency for the unit test! I think that is ok then.
I may or may not ditch the unit test in the future when I get annoyed by the extra compilation time.

[ppodolsky]

I may or may not ditch the unit test in the future when I get annoyed by the extra compilation time.

Sure, the test is mostly for illustrating the issue.

[fulmicoton]

Yes it is great!