Switch from failure to anyhow (#1851)

This commit switches all of `wasm-bindgen` from the `failure` crate to
`anyhow`. The `anyhow` crate should serve all the purposes that we
previously used `failure` for but has a few advantages:

* It's based on the standard `Error` trait rather than a custom `Fail`
  trait, improving ecosystem compatibility.
* We don't need a `#[derive(Fail)]`, which means that's less code to
  compile for `wasm-bindgen`. This notably helps the compile time of
  `web-sys` itself.
* Using `Result<()>` in `fn main` with `anyhow::Error` produces
  human-readable output, so we can use that natively.

crates/cli/src/bin/wasm-bindgen-test-runner/headless.rs

@@ -1,6 +1,6 @@
 use crate::shell::Shell;
+use anyhow::{bail, format_err, Context, Error};
 use curl::easy::Easy;
-use failure::{bail, format_err, Error, ResultExt};
 use log::{debug, warn};
 use rouille::url::Url;
 use serde::{Deserialize, Serialize};
@@ -138,8 +138,8 @@ pub fn run(server: &SocketAddr, shell: &Shell) -> Result<(), Error> {
     // We periodically check the page to see if the output contains a known
     // string to only be printed when tests have finished running.
     //
-    // TODO: harness failures aren't well handled here, they always force a
-    //       timeout. These sorts of failures could be "you typo'd the path to a
+    // TODO: harness anyhows aren't well handled here, they always force a
+    //       timeout. These sorts of anyhows could be "you typo'd the path to a
     //       local script" which is pretty bad to time out for, we should detect
     //       this on the page and look for such output here, printing diagnostic
     //       information.

crates/cli/src/bin/wasm-bindgen-test-runner/main.rs

@@ -11,11 +11,10 @@
 //! For more documentation about this see the `wasm-bindgen-test` crate README
 //! and source code.
 
-use failure::{bail, format_err, Error, ResultExt};
+use anyhow::{anyhow, bail, Context};
 use std::env;
 use std::fs;
 use std::path::PathBuf;
-use std::process;
 use std::thread;
 use wasm_bindgen_cli_support::Bindgen;
 
@@ -28,20 +27,8 @@ mod node;
 mod server;
 mod shell;
 
-fn main() {
+fn main() -> anyhow::Result<()> {
     env_logger::init();
-    let err = match rmain() {
-        Ok(()) => return,
-        Err(e) => e,
-    };
-    eprintln!("error: {}", err);
-    for cause in err.iter_causes() {
-        eprintln!("\tcaused by: {}", cause);
-    }
-    process::exit(1);
-}
-
-fn rmain() -> Result<(), Error> {
     let mut args = env::args_os().skip(1);
     let shell = shell::Shell::new();
 
@@ -59,7 +46,7 @@ fn rmain() -> Result<(), Error> {
         .and_then(|p| p.parent()) // chop off `deps`
         .and_then(|p| p.parent()) // chop off `debug`
         .map(|p| p.join("wbg-tmp"))
-        .ok_or_else(|| format_err!("file to test doesn't follow the expected Cargo conventions"))?;
+        .ok_or_else(|| anyhow!("file to test doesn't follow the expected Cargo conventions"))?;
 
     // Make sure there's no stale state from before
     drop(fs::remove_dir_all(&tmpdir));

crates/cli/src/bin/wasm-bindgen-test-runner/node.rs

@@ -4,7 +4,7 @@ use std::fs;
 use std::path::Path;
 use std::process::Command;
 
-use failure::{Error, ResultExt};
+use anyhow::{Context, Error};
 
 pub fn execute(
     module: &str,

crates/cli/src/bin/wasm-bindgen-test-runner/server.rs

@@ -3,7 +3,7 @@ use std::fs;
 use std::net::SocketAddr;
 use std::path::Path;
 
-use failure::{format_err, Error, ResultExt};
+use anyhow::{anyhow, Context, Error};
 use rouille::{Request, Response, Server};
 
 pub fn spawn(
@@ -90,7 +90,7 @@ pub fn spawn(
         response.headers.retain(|(k, _)| k != "Cache-Control");
         return response;
     })
-    .map_err(|e| format_err!("{}", e))?;
+    .map_err(|e| anyhow!("{}", e))?;
     return Ok(srv);
 
     fn try_asset(request: &Request, dir: &Path) -> Response {

crates/cli/src/bin/wasm-bindgen.rs

@@ -1,5 +1,5 @@
+use anyhow::{bail, Error};
 use docopt::Docopt;
-use failure::{bail, Error};
 use serde::Deserialize;
 use std::path::PathBuf;
 use std::process;
@@ -77,10 +77,7 @@ fn main() {
         Ok(()) => return,
         Err(e) => e,
     };
-    eprintln!("error: {}", err);
-    for cause in err.iter_causes() {
-        eprintln!("    caused by: {}", cause);
-    }
+    eprintln!("error: {:?}", err);
     process::exit(1);
 }
 

crates/cli/src/bin/wasm2es6js.rs

@@ -1,9 +1,8 @@
+use anyhow::{Context, Error};
 use docopt::Docopt;
-use failure::{Error, ResultExt};
 use serde::Deserialize;
 use std::fs;
 use std::path::PathBuf;
-use std::process;
 
 // no need for jemalloc bloat in this binary (and we don't need speed)
 #[global_allocator]
@@ -39,24 +38,12 @@ struct Args {
     arg_input: PathBuf,
 }
 
-fn main() {
+fn main() -> anyhow::Result<()> {
     let args: Args = Docopt::new(USAGE)
         .and_then(|d| d.deserialize())
         .unwrap_or_else(|e| e.exit());
-    let err = match rmain(&args) {
-        Ok(()) => return,
-        Err(e) => e,
-    };
-    eprintln!("error: {}", err);
-    for cause in err.iter_causes() {
-        eprintln!("\tcaused by: {}", cause);
-    }
-    process::exit(1);
-}
-
-fn rmain(args: &Args) -> Result<(), Error> {
     let wasm = fs::read(&args.arg_input)
-        .with_context(|_| format!("failed to read `{}`", args.arg_input.display()))?;
+        .with_context(|| format!("failed to read `{}`", args.arg_input.display()))?;
 
     let object = wasm_bindgen_cli_support::wasm2es6js::Config::new()
         .base64(args.flag_base64)
@@ -70,9 +57,9 @@ fn rmain(args: &Args) -> Result<(), Error> {
 
     let (js, wasm) = object.js_and_wasm()?;
 
-    write(args, "js", js.as_bytes(), false)?;
+    write(&args, "js", js.as_bytes(), false)?;
     if let Some(wasm) = wasm {
-        write(args, "wasm", &wasm, false)?;
+        write(&args, "wasm", &wasm, false)?;
     }
     Ok(())
 }
@@ -81,12 +68,12 @@ fn write(args: &Args, extension: &str, contents: &[u8], print_fallback: bool) ->
     if let Some(p) = &args.flag_output {
         let dst = p.with_extension(extension);
         fs::write(&dst, contents)
-            .with_context(|_| format!("failed to write `{}`", dst.display()))?;
+            .with_context(|| format!("failed to write `{}`", dst.display()))?;
     } else if let Some(p) = &args.flag_out_dir {
         let filename = args.arg_input.file_name().unwrap();
         let dst = p.join(filename).with_extension(extension);
         fs::write(&dst, contents)
-            .with_context(|_| format!("failed to write `{}`", dst.display()))?;
+            .with_context(|| format!("failed to write `{}`", dst.display()))?;
     } else if print_fallback {
         println!("{}", String::from_utf8_lossy(contents))
     }