Why .full() and .json() are not present for tracing_subscriber::fmt() when .pretty() and .compact() are?

[frederikhors]

I'm using this code instead of using registry:

tracing_subscriber::fmt()
  // .full() // this method is not present
  // .compact()
  // .pretty()
  // .json() // this method is not present
  .init();

Why those methods are not present?

[davidbarsky]

While .full() is already the default state of the builder returned by tracing_subscriber::fmt(), we should probably have that method for consistency's sake. .json() is present: did you enable the JSON feature in your Cargo.toml?

[frederikhors]

Now only this is the remaining question, if you can help me better understand:

A quick question: it's fine to use tracing_subscriber::fmt().init() directly or should I use registry with tracing_subscriber::fmt::layer()?

[davidbarsky]

yes, sorry! it's totally fine to use tracing_subscriber::fmt().init() instead of fmt::Layer() + the registry. init() does a few more things depending on Cargo's feature flags (sets up log integration and EnvFilter are the big ones), but it's possible to setup these with layers and the registry. the biggest advantage of using fmt::Layer and the Registry is that it makes it easy to add additional layers, such as tracing-opentelemetry or tracing-chrome. In other words, it's a lower-level API, but a more flexible one.

[CEbbinghaus]

Sorry to necro this post but I am banging my head against the wall to get this working.
If I use tracing-subscriber without any dependencies it fails to find the json method (ofc coz its a crate feature):
tracing-subscriber = "0.3.18"

error[E0599]: no method named `json` found for struct `SubscriberBuilder` in the current scope
  --> src/log.rs:12:50
   |
12 |     let mut file_writer = tracing_subscriber::fmt().json().with_writer(file);
   |                                                     ^^^^ method not found in `SubscriberBuilder`

However enabling the feature causes completely different (already functioning) methods to break:
tracing-subscriber = { version = "0.3.18", features = ["default", "json"] } (the default is there for sanity)

error[E0599]: no method named `set_ansi` found for struct `SubscriberBuilder` in the current scope
  --> src/log.rs:14:14
   |
14 |     file_writer.set_ansi(false);
   |                 ^^^^^^^^ method not found in `SubscriberBuilder<JsonFields, Format<Json>, LevelFilter, File>`

error[E0599]: no method named `with_filter` found for struct `SubscriberBuilder` in the current scope
  --> src/log.rs:18:16
   |
18 |             file_writer.with_filter(tracing_subscriber::filter::LevelFilter::from_level(CONFIG.log_level))
   |                         ^^^^^^^^^^^ help: there is a method with a similar name: `with_file`

This also happens when I go overboard and enable all features at once:

tracing-subscriber = { version = "0.3.18", features = [
    "default",
    "alloc",
    "std",
    "env-filter",
    "fmt",
    "ansi",
    "registry",
    "json",
] }

I'm at my witts end. No idea why enabling Json breaks everything else

[mladedav]

@CEbbinghaus could you share the code? Are you absolutely sure you're using the same versions?

[CEbbinghaus]

I am using the same version, Although I since managed to figure it out with the help of a Rust community member. What I had not considered is that By changing the code to use the json() method I had to change the namespace & therefore the type of the instance. As such they were valid errors that just appeared invalid as the type they were on was different. That was 110% my fault for not recognizing the failures as genuine failures due to bad code and not as failures of the library.

Here is the change in question although it was after I had figured it out & therefore is very small:
CEbbinghaus/MicroSDeck@7a2fdf3