Replace anyhow dependency with a handwritten reporter

BUCK

@@ -16,7 +16,6 @@ rust_binary(
     crate = "cxxbridge",
     visibility = ["PUBLIC"],
     deps = [
-        "//third-party:anyhow",
         "//third-party:clap",
         "//third-party:codespan-reporting",
         "//third-party:proc-macro2",
@@ -60,7 +59,6 @@ rust_library(
     srcs = glob(["gen/build/src/**"]),
     visibility = ["PUBLIC"],
     deps = [
-        "//third-party:anyhow",
         "//third-party:cc",
         "//third-party:codespan-reporting",
         "//third-party:proc-macro2",
@@ -74,7 +72,6 @@ rust_library(
     srcs = glob(["gen/lib/src/**"]),
     visibility = ["PUBLIC"],
     deps = [
-        "//third-party:anyhow",
         "//third-party:cc",
         "//third-party:codespan-reporting",
         "//third-party:proc-macro2",

BUILD

@@ -19,7 +19,6 @@ rust_binary(
     data = ["gen/cmd/src/gen/include/cxx.h"],
     visibility = ["//visibility:public"],
     deps = [
-        "//third-party:anyhow",
         "//third-party:clap",
         "//third-party:codespan-reporting",
         "//third-party:proc-macro2",
@@ -59,7 +58,6 @@ rust_library(
     data = ["gen/build/src/gen/include/cxx.h"],
     visibility = ["//visibility:public"],
     deps = [
-        "//third-party:anyhow",
         "//third-party:cc",
         "//third-party:codespan-reporting",
         "//third-party:proc-macro2",
@@ -74,7 +72,6 @@ rust_library(
     data = ["gen/lib/src/gen/include/cxx.h"],
     visibility = ["//visibility:public"],
     deps = [
-        "//third-party:anyhow",
         "//third-party:cc",
         "//third-party:codespan-reporting",
         "//third-party:proc-macro2",

gen/build/Cargo.toml

@@ -10,7 +10,6 @@ keywords = ["ffi"]
 categories = ["development-tools::ffi"]
 
 [dependencies]
-anyhow = "1.0"
 cc = "1.0.49"
 codespan-reporting = "0.9"
 proc-macro2 = { version = "1.0.17", default-features = false, features = ["span-locations"] }

gen/build/src/lib.rs

@@ -58,8 +58,8 @@ mod paths;
 mod syntax;
 
 use crate::error::Result;
+use crate::gen::error::report;
 use crate::gen::Opt;
-use anyhow::anyhow;
 use std::fs;
 use std::io::{self, Write};
 use std::iter;
@@ -93,7 +93,7 @@ pub fn bridges(rust_source_files: impl IntoIterator<Item = impl AsRef<Path>>) ->
 
     for path in rust_source_files {
         if let Err(err) = try_generate_bridge(&mut build, path.as_ref()) {
-            let _ = writeln!(io::stderr(), "\n\ncxxbridge error: {:?}\n\n", anyhow!(err));
+            let _ = writeln!(io::stderr(), "\n\ncxxbridge error: {}\n\n", report(err));
             process::exit(1);
         }
     }

gen/cmd/Cargo.toml

@@ -14,7 +14,6 @@ name = "cxxbridge"
 path = "src/main.rs"
 
 [dependencies]
-anyhow = "1.0"
 clap = "2.33"
 codespan-reporting = "0.9"
 proc-macro2 = { version = "1.0.17", default-features = false, features = ["span-locations"] }

gen/lib/Cargo.toml

@@ -10,7 +10,6 @@ keywords = ["ffi"]
 categories = ["development-tools::ffi"]
 
 [dependencies]
-anyhow = "1.0"
 cc = "1.0.49"
 codespan-reporting = "0.9"
 proc-macro2 = { version = "1.0.17", default-features = false, features = ["span-locations"] }

gen/src/error.rs

@@ -1,5 +1,4 @@
 use crate::syntax;
-use anyhow::anyhow;
 use codespan_reporting::diagnostic::{Diagnostic, Label};
 use codespan_reporting::files::SimpleFiles;
 use codespan_reporting::term::termcolor::{ColorChoice, StandardStream, WriteColor};
@@ -63,11 +62,34 @@ pub(super) fn format_err(path: &Path, source: &str, error: Error) -> ! {
                 display_syn_error(stderr, path, source, error);
             }
         }
-        _ => eprintln!("cxxbridge: {:?}", anyhow!(error)),
+        _ => {
+            let _ = writeln!(io::stderr(), "cxxbridge: {}", report(error));
+        }
     }
     process::exit(1);
 }
 
+pub(crate) fn report(error: impl StdError) -> impl Display {
+    struct Report<E>(E);
+
+    impl<E: StdError> Display for Report<E> {
+        fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+            Display::fmt(&self.0, formatter)?;
+            let mut error: &dyn StdError = &self.0;
+
+            while let Some(cause) = error.source() {
+                formatter.write_str("\n\nCaused by:\n    ")?;
+                Display::fmt(cause, formatter)?;
+                error = cause;
+            }
+
+            Ok(())
+        }
+    }
+
+    Report(error)
+}
+
 fn sort_syn_errors(error: syn::Error) -> Vec<syn::Error> {
     let mut errors: Vec<_> = error.into_iter().collect();
     errors.sort_by_key(|e| {

gen/src/mod.rs

@@ -1,7 +1,7 @@
 // Functionality that is shared between the cxx_build::bridge entry point and
 // the cxxbridge CLI command.
 
-mod error;
+pub(super) mod error;
 mod file;
 pub(super) mod include;
 pub(super) mod out;

third-party/BUCK

@@ -1,12 +1,5 @@
 # To be generated by Facebook's `reindeer` tool once that is open source.
 
-rust_library(
-    name = "anyhow",
-    srcs = glob(["vendor/anyhow-1.0.32/src/**"]),
-    visibility = ["PUBLIC"],
-    features = ["std"],
-)
-
 rust_library(
     name = "bitflags",
     srcs = glob(["vendor/bitflags-1.2.1/src/**"]),

third-party/BUILD

@@ -5,13 +5,6 @@ load(
 )
 load("@bazel_tools//tools/build_defs/pkg:pkg.bzl", "pkg_tar")
 
-rust_library(
-    name = "anyhow",
-    srcs = glob(["vendor/anyhow-1.0.32/src/**"]),
-    crate_features = ["std"],
-    visibility = ["//visibility:public"],
-)
-
 rust_library(
     name = "bitflags",
     srcs = glob(["vendor/bitflags-1.2.1/src/**"]),

third-party/Cargo.lock

@@ -9,12 +9,6 @@ dependencies = [
  "winapi",
 ]
 
-[[package]]
-name = "anyhow"
-version = "1.0.32"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "6b602bfe940d21c130f3895acd65221e8a61270debe89d628b9cb4e3ccb8569b"
-
 [[package]]
 name = "atty"
 version = "0.2.14"
@@ -81,7 +75,6 @@ dependencies = [
 name = "cxx-build"
 version = "0.3.7"
 dependencies = [
- "anyhow",
  "cc",
  "codespan-reporting",
  "cxx-gen",
@@ -94,7 +87,6 @@ dependencies = [
 name = "cxx-gen"
 version = "0.0.1"
 dependencies = [
- "anyhow",
  "cc",
  "codespan-reporting",
  "proc-macro2",
@@ -115,7 +107,6 @@ dependencies = [
 name = "cxxbridge-cmd"
 version = "0.3.7"
 dependencies = [
- "anyhow",
  "clap",
  "codespan-reporting",
  "proc-macro2",