Switch from failure to anyhow.

  - Use the anyhow crate instead of failure to implement the dynamic
    side of our error handling.  anyhow::Error derefs to dyn
    std::error::Error, allowing better interoperability with other
    stdlib-based error handling libraries.

  - Fixes #444.

6 files changed, 36 insertions, 67 deletions

diff --git a/tool/Cargo.toml b/tool/Cargo.toml
index 10832d54..3139bc9a 100644
--- a/tool/Cargo.toml
+++ b/tool/Cargo.toml
@@ -27,9 +27,9 @@ sequoia-autocrypt = { path = "../autocrypt", version = "0.15" }
 sequoia-core = { path = "../core", version = "0.15" }
 sequoia-net = { path = "../net", version = "0.15" }
 sequoia-store = { path = "../store", version = "0.15" }
+anyhow = "1"
 chrono = "0.4"
 clap = "2.32.0"
-failure = "0.1.2"
 itertools = "0.8"
 prettytable-rs = "0.8.0"
 rpassword = "=4.0.3"
diff --git a/tool/src/commands/decrypt.rs b/tool/src/commands/decrypt.rs
index 65b9d579..964fd6c8 100644
--- a/tool/src/commands/decrypt.rs
+++ b/tool/src/commands/decrypt.rs
@@ -1,5 +1,5 @@
 use crossterm::terminal;
-use failure::{self, ResultExt};
+use anyhow::Context as _;
 use std::collections::HashMap;
 use std::io;
 use rpassword;
@@ -253,7 +253,7 @@ impl<'a> DecryptionHelper for Helper<'a> {
 
         if skesks.is_empty() {
             return
-                Err(failure::err_msg("No key to decrypt message"));
+                Err(anyhow::anyhow!("No key to decrypt message"));
         }
 
         // Finally, try to decrypt using the SKESKs.
@@ -289,14 +289,7 @@ pub fn decrypt(ctx: &Context, policy: &dyn Policy, mapping: &mut store::Mapping,
     let mut decryptor = Decryptor::from_reader(policy, input, helper, None)
         .context("Decryption failed")?;
 
-    io::copy(&mut decryptor, output)
-        .map_err(|e| if e.get_ref().is_some() {
-            // Wrapped failure::Error.  Recover it.
-            failure::Error::from_boxed_compat(e.into_inner().unwrap())
-        } else {
-            // Plain io::Error.
-            e.into()
-        }).context("Decryption failed")?;
+    io::copy(&mut decryptor, output).context("Decryption failed")?;
 
     let helper = decryptor.into_helper();
     if let Some(dumper) = helper.dumper.as_ref() {
diff --git a/tool/src/commands/key.rs b/tool/src/commands/key.rs
index bbde9ceb..688633a8 100644
--- a/tool/src/commands/key.rs
+++ b/tool/src/commands/key.rs
@@ -1,5 +1,4 @@
-use failure;
-use failure::Fail;
+use anyhow::Context as _;
 use clap::ArgMatches;
 use itertools::Itertools;
 use std::time::{SystemTime, Duration};
@@ -66,7 +65,7 @@ pub fn generate(m: &ArgMatches, force: bool) -> Result<()> {
             builder = builder.set_cipher_suite(CipherSuite::Cv25519);
         }
         Some(ref cs) => {
-            return Err(format_err!("Unknown cipher suite '{}'", cs));
+            return Err(anyhow::anyhow!("Unknown cipher suite '{}'", cs));
         }
         None => panic!("argument has a default value"),
     }
@@ -79,7 +78,7 @@ pub fn generate(m: &ArgMatches, force: bool) -> Result<()> {
         (false, true) => { /* no signing subkey */ }
         (true, true) => {
             return Err(
-                format_err!("Conflicting arguments --can-sign and --cannot-sign"));
+                anyhow::anyhow!("Conflicting arguments --can-sign and --cannot-sign"));
         }
     }
 
@@ -101,12 +100,12 @@ pub fn generate(m: &ArgMatches, force: bool) -> Result<()> {
         (None, true) => { /* no encryption subkey */ }
         (Some(_), true) => {
             return Err(
-                format_err!("Conflicting arguments --can-encrypt and \
+                anyhow::anyhow!("Conflicting arguments --can-encrypt and \
                              --cannot-encrypt"));
         }
         (Some(ref cap), false) => {
             return Err(
-                format_err!("Unknown encryption capability '{}'", cap));
+                anyhow::anyhow!("Unknown encryption capability '{}'", cap));
         }
     }
 
@@ -119,7 +118,7 @@ pub fn generate(m: &ArgMatches, force: bool) -> Result<()> {
         if p0 == p1 {
             builder = builder.set_password(Some(p0));
         } else {
-            return Err(failure::err_msg("Passwords do not match."));
+            return Err(anyhow::anyhow!("Passwords do not match."));
         }
     }
 
@@ -136,7 +135,7 @@ pub fn generate(m: &ArgMatches, force: bool) -> Result<()> {
                     ("-".to_string(), rp.to_string()),
                 (Some("-"), None) =>
                     return Err(
-                        format_err!("Missing arguments: --rev-cert is mandatory \
+                        anyhow::anyhow!("Missing arguments: --rev-cert is mandatory \
                                      if --export is '-'.")),
                 (Some(ref kp), None) =>
                     (kp.to_string(), format!("{}.rev", kp)),
@@ -146,7 +145,7 @@ pub fn generate(m: &ArgMatches, force: bool) -> Result<()> {
                     (kp.to_string(), rp.to_string()),
                 _ =>
                     return Err(
-                        format_err!("Conflicting arguments --rev-cert and \
+                        anyhow::anyhow!("Conflicting arguments --rev-cert and \
                                      --export")),
             };
 
@@ -178,7 +177,7 @@ pub fn generate(m: &ArgMatches, force: bool) -> Result<()> {
         }
     } else {
         return Err(
-            format_err!("Saving generated key to the store isn't implemented \
+            anyhow::anyhow!("Saving generated key to the store isn't implemented \
                          yet."));
     }
 
@@ -205,19 +204,18 @@ fn parse_duration(expiry: &str) -> Result<Duration> {
     let junk = expiry.collect::<String>();
 
     if digits == "" {
-        return Err(format_err!(
+        return Err(anyhow::anyhow!(
             "--expiry: missing count \
              (try: '2y' for 2 years)"));
     }
 
     let count = match digits.parse::<i32>() {
         Ok(count) if count < 0 =>
-            return Err(format_err!(
+            return Err(anyhow::anyhow!(
                 "--expiry: Expiration can't be in the past")),
         Ok(count) => count as u64,
         Err(err) =>
-            return Err(err.context(
-                "--expiry: count is out of range").into()),
+            return Err(err).context("--expiry: count is out of range"),
     };
 
     let factor = match suffix {
@@ -226,19 +224,19 @@ fn parse_duration(expiry: &str) -> Result<Duration> {
         Some('w') | Some('W') => 7 * SECONDS_IN_DAY,
         Some('d') | Some('D') => SECONDS_IN_DAY,
         None =>
-            return Err(format_err!(
+            return Err(anyhow::anyhow!(
                 "--expiry: missing suffix \
                  (try: '{}y', '{}m', '{}w' or '{}d' instead)",
                 digits, digits, digits, digits)),
         Some(suffix) =>
-            return Err(format_err!(
+            return Err(anyhow::anyhow!(
                 "--expiry: invalid suffix '{}' \
                  (try: '{}y', '{}m', '{}w' or '{}d' instead)",
                 suffix, digits, digits, digits, digits)),
     };
 
     if junk != "" {
-        return Err(format_err!(
+        return Err(anyhow::anyhow!(
             "--expiry: contains trailing junk ('{:?}') \
              (try: '{}{}')",
             junk, count, factor));
diff --git a/tool/src/commands/mod.rs b/tool/src/commands/mod.rs
index a925d362..8c2fd516 100644
--- a/tool/src/commands/mod.rs
+++ b/tool/src/commands/mod.rs
@@ -1,4 +1,4 @@
-use failure::{self, ResultExt};
+use anyhow::Context as _;
 use std::cmp::Ordering;
 use std::collections::{HashMap, HashSet};
 use std::fs::File;
@@ -78,7 +78,7 @@ fn get_signing_keys(certs: &[openpgp::Cert], p: &dyn Policy,
             }
         }
 
-        return Err(failure::err_msg(
+        return Err(anyhow::anyhow!(
             format!("Found no suitable signing key on {}", tsk)));
     }
 
@@ -108,7 +108,7 @@ pub fn encrypt(policy: &dyn Policy,
     }
 
     if certs.len() + passwords.len() == 0 {
-        return Err(failure::format_err!(
+        return Err(anyhow::anyhow!(
             "Neither recipient nor password given"));
     }
 
@@ -128,7 +128,7 @@ pub fn encrypt(policy: &dyn Policy,
             count += 1;
         }
         if count == 0 {
-            return Err(failure::format_err!(
+            return Err(anyhow::anyhow!(
                 "Key {} has no suitable encryption key", cert));
         }
     }
@@ -394,7 +394,7 @@ impl<'a> VerificationHelper for VHelper<'a> {
             Ok(())
         } else {
             self.print_status();
-            Err(failure::err_msg("Verification failed"))
+            Err(anyhow::anyhow!("Verification failed"))
         }
     }
 }
@@ -413,14 +413,7 @@ pub fn verify(ctx: &Context, policy: &dyn Policy,
         Verifier::from_reader(policy, input, helper, None)?
     };
 
-    io::copy(&mut verifier, output)
-        .map_err(|e| if e.get_ref().is_some() {
-            // Wrapped failure::Error.  Recover it.
-            failure::Error::from_boxed_compat(e.into_inner().unwrap())
-        } else {
-            // Plain io::Error.
-            e.into()
-        })?;
+    io::copy(&mut verifier, output)?;
 
     verifier.into_helper().print_status();
     Ok(())
diff --git a/tool/src/commands/sign.rs b/tool/src/commands/sign.rs
index 89b97a10..9a8e6819 100644
--- a/tool/src/commands/sign.rs
+++ b/tool/src/commands/sign.rs
@@ -1,4 +1,4 @@
-use failure::{self, ResultExt};
+use anyhow::Context as _;
 use std::fs;
 use std::io;
 use std::path::PathBuf;
@@ -60,7 +60,7 @@ fn sign_data(policy: &dyn Policy,
                 match packet {
                     Packet::Signature(sig) => sigs.push(sig),
                     p => return Err(
-                        failure::err_msg(
+                        anyhow::anyhow!(
                             format!("{} in detached signature", p.tag()))
                             .context("Invalid detached signature").into()),
                 }
@@ -91,7 +91,7 @@ fn sign_data(policy: &dyn Policy,
 
     let mut keypairs = super::get_signing_keys(&secrets, policy, time)?;
     if keypairs.is_empty() {
-        return Err(failure::format_err!("No signing keys found"));
+        return Err(anyhow::anyhow!("No signing keys found"));
     }
 
     // When extending a detached signature, prepend any existing
@@ -166,7 +166,7 @@ fn sign_message_(policy: &dyn Policy,
 {
     let mut keypairs = super::get_signing_keys(&secrets, policy, time)?;
     if keypairs.is_empty() {
-        return Err(failure::format_err!("No signing keys found"));
+        return Err(anyhow::anyhow!("No signing keys found"));
     }
 
     let mut sink = Message::new(output);
@@ -205,7 +205,7 @@ fn sign_message_(policy: &dyn Policy,
 
         match pp.packet {
             Packet::PKESK(_) | Packet::SKESK(_) =>
-                return Err(failure::err_msg(
+                return Err(anyhow::anyhow!(
                     "Signing encrypted data is not implemented")),
 
             Packet::Literal(_) =>
@@ -223,7 +223,7 @@ fn sign_message_(policy: &dyn Policy,
             // If you do implement this, there is a half-disabled test
             // in tests/sq-sign.rs.
             Packet::CompressedData(_) if seen_signature =>
-                return Err(failure::err_msg(
+                return Err(anyhow::anyhow!(
                     "Signing a compress-then-sign message is not implemented")),
 
             _ => (),
diff --git a/tool/src/sq.rs b/tool/src/sq.rs
index 6b188e0e..421dadae 100644
--- a/tool/src/sq.rs
+++ b/tool/src/sq.rs
@@ -2,8 +2,6 @@
 
 extern crate clap;
 #[macro_use]
-extern crate failure;
-#[macro_use]
 extern crate prettytable;
 extern crate rpassword;
 extern crate tempfile;
@@ -12,7 +10,7 @@ extern crate itertools;
 extern crate tokio_core;
 
 use crossterm::terminal;
-use failure::ResultExt;
+use anyhow::Context as _;
 use prettytable::{Table, Cell, Row};
 use std::fs::{File, OpenOptions};
 use std::io::{self, Write};
@@ -65,7 +63,7 @@ fn create_or_stdout(f: Option<&str>, force: bool)
                             .open(f)
                             .context("Failed to create output file")?))
             } else {
-                Err(failure::err_msg(
+                Err(anyhow::anyhow!(
                     format!("File {:?} exists, use --force to overwrite", p)))
             }
         }
@@ -213,7 +211,7 @@ fn help_warning(arg: &str) {
     }
 }
 
-fn real_main() -> Result<()> {
+fn main() -> Result<()> {
     let policy = &P::new();
 
     let matches = sq_cli::build().get_matches();
@@ -392,7 +390,7 @@ fn real_main() -> Result<()> {
                     let ac = autocrypt::AutocryptHeader::new_sender(
                         policy,
                         &cert,
-                        &addr.ok_or(failure::err_msg(
+                        &addr.ok_or(anyhow::anyhow!(
                             "No well-formed primary userid found, use \
                              --address to specify one"))?,
                         m.value_of("prefer-encrypt").expect("has default"))?;
@@ -767,7 +765,7 @@ fn parse_iso8601(s: &str, pad_date_with: chrono::NaiveTime)
             return Ok(DateTime::from_utc(d.and_time(pad_date_with), Utc));
         }
     }
-    Err(failure::format_err!("Malformed ISO8601 timestamp: {}", s))
+    Err(anyhow::anyhow!("Malformed ISO8601 timestamp: {}", s))
 }
 
 #[test]
@@ -795,16 +793,3 @@ fn test_parse_iso8601() {
     parse_iso8601("2017031", z).unwrap();
     // parse_iso8601("2017", z).unwrap(); // ditto
 }
-
-fn main() {
-    if let Err(e) = real_main() {
-        let mut cause = e.as_fail();
-        eprint!("{}", cause);
-        while let Some(c) = cause.cause() {
-            eprint!(":\n  {}", c);
-            cause = c;
-        }
-        eprintln!();
-        exit(2);
-    }
-}