tower_layer/
stack.rs

1use super::Layer;
2use std::fmt;
3
4/// Two middlewares chained together.
5#[derive(Clone)]
6pub struct Stack<Inner, Outer> {
7    inner: Inner,
8    outer: Outer,
9}
10
11impl<Inner, Outer> Stack<Inner, Outer> {
12    /// Create a new `Stack`.
13    pub const fn new(inner: Inner, outer: Outer) -> Self {
14        Stack { inner, outer }
15    }
16}
17
18impl<S, Inner, Outer> Layer<S> for Stack<Inner, Outer>
19where
20    Inner: Layer<S>,
21    Outer: Layer<Inner::Service>,
22{
23    type Service = Outer::Service;
24
25    fn layer(&self, service: S) -> Self::Service {
26        let inner = self.inner.layer(service);
27
28        self.outer.layer(inner)
29    }
30}
31
32impl<Inner, Outer> fmt::Debug for Stack<Inner, Outer>
33where
34    Inner: fmt::Debug,
35    Outer: fmt::Debug,
36{
37    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
38        // The generated output of nested `Stack`s is very noisy and makes
39        // it harder to understand what is in a `ServiceBuilder`.
40        //
41        // Instead, this output is designed assuming that a `Stack` is
42        // usually quite nested, and inside a `ServiceBuilder`. Therefore,
43        // this skips using `f.debug_struct()`, since each one would force
44        // a new layer of indentation.
45        //
46        // - In compact mode, a nested stack ends up just looking like a flat
47        //   list of layers.
48        //
49        // - In pretty mode, while a newline is inserted between each layer,
50        //   the `DebugStruct` used in the `ServiceBuilder` will inject padding
51        //   to that each line is at the same indentation level.
52        //
53        // Also, the order of [outer, inner] is important, since it reflects
54        // the order that the layers were added to the stack.
55        if f.alternate() {
56            // pretty
57            write!(f, "{:#?},\n{:#?}", self.outer, self.inner)
58        } else {
59            write!(f, "{:?}, {:?}", self.outer, self.inner)
60        }
61    }
62}
tower_layer/stack.rs

tower_layer/
stack.rs
