Struct tracing_subscriber::fmt::TestWriter

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pub struct TestWriter { /* private fields */ }
Expand description

A writer intended to support libtest’s output capturing for use in unit tests.

TestWriter is used by fmt::Subscriber or fmt::Layer to enable capturing support.

cargo test can only capture output from the standard library’s print! macro. See libtest’s output capturing for more details about output capturing.

Writing to io::stdout and io::stderr produces the same results as using libtest’s --nocapture option which may make the results look unreadable.

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impl TestWriter

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pub fn new() -> Self

Returns a new TestWriter with the default configuration.

Trait Implementations§

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impl Debug for TestWriter

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fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter. Read more
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impl Default for TestWriter

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fn default() -> TestWriter

Returns the “default value” for a type. Read more
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impl<'a> MakeWriter<'a> for TestWriter

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type Writer = TestWriter

The concrete io::Write implementation returned by make_writer.
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fn make_writer(&'a self) -> Self::Writer

Returns an instance of Writer. Read more
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fn make_writer_for(&'a self, meta: &Metadata<'_>) -> Self::Writer

Returns a Writer for writing data from the span or event described by the provided Metadata. Read more
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impl Write for TestWriter

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fn write(&mut self, buf: &[u8]) -> Result<usize>

Write a buffer into this writer, returning how many bytes were written. Read more
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fn flush(&mut self) -> Result<()>

Flush this output stream, ensuring that all intermediately buffered contents reach their destination. Read more
1.36.0 · source§

fn write_vectored(&mut self, bufs: &[IoSlice<'_>]) -> Result<usize, Error>

Like write, except that it writes from a slice of buffers. Read more
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fn is_write_vectored(&self) -> bool

🔬This is a nightly-only experimental API. (can_vector #69941)
Determines if this Writer has an efficient write_vectored implementation. Read more
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fn write_all(&mut self, buf: &[u8]) -> Result<(), Error>

Attempts to write an entire buffer into this writer. Read more
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fn write_all_vectored(&mut self, bufs: &mut [IoSlice<'_>]) -> Result<(), Error>

🔬This is a nightly-only experimental API. (write_all_vectored #70436)
Attempts to write multiple buffers into this writer. Read more
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fn write_fmt(&mut self, fmt: Arguments<'_>) -> Result<(), Error>

Writes a formatted string into this writer, returning any error encountered. Read more
1.0.0 · source§

fn by_ref(&mut self) -> &mut Self
where Self: Sized,

Creates a “by reference” adapter for this instance of Write. Read more

Auto Trait Implementations§

Blanket Implementations§

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impl<T> Any for T
where T: 'static + ?Sized,

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fn type_id(&self) -> TypeId

Gets the TypeId of self. Read more
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impl<T> Borrow<T> for T
where T: ?Sized,

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fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more
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impl<T> BorrowMut<T> for T
where T: ?Sized,

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fn borrow_mut(&mut self) -> &mut T

Mutably borrows from an owned value. Read more
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impl<T> From<T> for T

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fn from(t: T) -> T

Returns the argument unchanged.

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impl<T> Instrument for T

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fn instrument(self, span: Span) -> Instrumented<Self>

Instruments this type with the provided Span, returning an Instrumented wrapper. Read more
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fn in_current_span(self) -> Instrumented<Self>

Instruments this type with the current Span, returning an Instrumented wrapper. Read more
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impl<T, U> Into<U> for T
where U: From<T>,

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fn into(self) -> U

Calls U::from(self).

That is, this conversion is whatever the implementation of From<T> for U chooses to do.

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impl<'a, M> MakeWriterExt<'a> for M
where M: MakeWriter<'a>,

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fn with_max_level(self, level: Level) -> WithMaxLevel<Self>
where Self: Sized,

Wraps self and returns a MakeWriter that will only write output for events at or below the provided verbosity Level. For instance, Level::TRACE is considered to be _more verbosethanLevel::INFO`. Read more
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fn with_min_level(self, level: Level) -> WithMinLevel<Self>
where Self: Sized,

Wraps self and returns a MakeWriter that will only write output for events at or above the provided verbosity Level. Read more
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fn with_filter<F>(self, filter: F) -> WithFilter<Self, F>
where Self: Sized, F: Fn(&Metadata<'_>) -> bool,

Wraps self with a predicate that takes a span or event’s Metadata and returns a bool. The returned MakeWriter’s MakeWriter::make_writer_for method will check the predicate to determine if a writer should be produced for a given span or event. Read more
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fn and<B>(self, other: B) -> Tee<Self, B>
where Self: Sized, B: MakeWriter<'a> + Sized,

Combines self with another type implementing MakeWriter, returning a new MakeWriter that produces writers that write to both outputs. Read more
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fn or_else<W, B>(self, other: B) -> OrElse<Self, B>
where Self: MakeWriter<'a, Writer = OptionalWriter<W>> + Sized, B: MakeWriter<'a> + Sized, W: Write,

Combines self with another type implementing MakeWriter, returning a new MakeWriter that calls other’s make_writer if self’s make_writer returns OptionalWriter::none. Read more
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impl<T, U> TryFrom<U> for T
where U: Into<T>,

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type Error = Infallible

The type returned in the event of a conversion error.
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fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

Performs the conversion.
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impl<T, U> TryInto<U> for T
where U: TryFrom<T>,

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type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.
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fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>

Performs the conversion.
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impl<T> WithSubscriber for T

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fn with_subscriber<S>(self, subscriber: S) -> WithDispatch<Self>
where S: Into<Dispatch>,

Attaches the provided Subscriber to this type, returning a WithDispatch wrapper. Read more
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fn with_current_subscriber(self) -> WithDispatch<Self>

Attaches the current default Subscriber to this type, returning a WithDispatch wrapper. Read more