Improve formatting of e2e test build errors

[itowlson]

I was editing testcases/key-value/lib.rs and missed a ? on a fallible operation and this is how make test-kv explained the problem to me:

It would be great if we could preserve line breaks to make errors like this easier to read.

[rajatjindal]

Hi @itowlson

sorry about this. I am looking into this.

would something like following be fine:

running 1 test
stderr: 
[
    "   Compiling key-value v0.1.0 (/Users/rajatjindal/go/src/github.com/fermyon/spin/tests/testcases/key-value)",
    "error[E0277]: can't compare `[_]` with `Result<Vec<u8>, key_value::key_value::Error>`",
    "  --> src/lib.rs:26:28",
    "   |",
    "26 |     ensure!(b\"baz\" as &[_] == &store.get(\"bar\"));",
    "   |                            ^^ no implementation for `[_] == Result<Vec<u8>, key_value::key_value::Error>`",
    "   |",
    "   = help: the trait `PartialEq<Result<Vec<u8>, key_value::key_value::Error>>` is not implemented for `[_]`",
    "   = help: the following other types implement trait `PartialEq<Rhs>`:",
    "             <&[B] as PartialEq<[A; N]>>",
    "             <&[T] as PartialEq<Vec<U, A>>>",
    "             <&[u8] as PartialEq<BytesMut>>",
    "             <&[u8] as PartialEq<bytes::Bytes>>",
    "             <&mut [B] as PartialEq<[A; N]>>",
    "             <&mut [T] as PartialEq<Vec<U, A>>>",
    "             <[A; N] as PartialEq<&[B]>>",
    "             <[A; N] as PartialEq<&mut [B]>>",
    "           and 8 others",
    "   = note: required for `&[_]` to implement `PartialEq<&Result<Vec<u8>, key_value::key_value::Error>>`",
    "   = note: 1 redundant requirement hidden",
    "   = note: required for `&&[_]` to implement `~const PartialEq<&&Result<Vec<u8>, key_value::key_value::Error>>`",
    "",
    "For more information about this error, try `rustc --explain E0277`.",
    "error: could not compile `key-value` (lib) due to previous error",
    "Error: Build command for component hello failed with status Exited(101)",
]
stdout: 
[
    "Executing the build command for component hello: cargo build --release --target wasm32-wasi",
]

I am getting above using

println!(
            "stderr: \n{:#?}",
            std::str::from_utf8(&output.stderr)?
                .lines()
                .collect::<Vec<&str>>()
        );

If there is a better way to do this, could you please let me know. thanks

[itowlson]

Yep, that would be fine - thanks!