search bitcoind executable also in the PATH

when neither BITCOIND_EXE env var or feature is set, this looks for bitcoind
executable in the PATH

Author: RCasatta

Cargo.toml

@@ -13,6 +13,7 @@ bitcoincore-rpc = "0.14.0"
 tempfile = "3.1"
 log = "0.4"
 home = "0.5.3"  # use same ver in build-dep
+which = "4.2.5"
 
 [dev-dependencies]
 env_logger = "0.8"

README.md

@@ -7,7 +7,8 @@ Utility to run a regtest bitcoind process, useful in integration testing environ
 
 ```rust
 use bitcoincore_rpc::RpcApi;
-let bitcoind = bitcoind::BitcoinD::new("/usr/local/bin/bitcoind").unwrap();
+let exe_path = exe_path().expect("bitcoind executable must be provided in BITCOIND_EXE, or with a feature like '22_0', or be in PATH");
+let bitcoind = bitcoind::BitcoinD::new(exe_path).unwrap();
 assert_eq!(0, bitcoind.client.get_blockchain_info().unwrap().blocks);
 ```
 

src/lib.rs

@@ -95,8 +95,9 @@ pub enum Error {
     NoFeature,
     /// Returned when calling methods requiring a env var to exist, but it's not
     NoEnvVar,
-    /// Returned when calling methods requiring either a feature or env var, but both are absent
-    NeitherFeatureNorEnvVar,
+    /// Returned when calling methods requiring the bitcoind executable but none is found
+    /// (no feature, no `BITCOIND_EXE`, no `bitcoind` in `PATH` )
+    NoBitcoindExecutableFound,
     /// Returned when calling methods requiring either a feature or anv var, but both are present
     BothFeatureAndEnvVar,
     /// Wrapper of early exit status
@@ -112,7 +113,7 @@ impl fmt::Debug for Error {
             Error::Rpc(e) => write!(f, "{:?}", e),
             Error::NoFeature => write!(f, "Called a method requiring a feature to be set, but it's not"),
             Error::NoEnvVar => write!(f, "Called a method requiring env var `BITCOIND_EXE` to be set, but it's not"),
-            Error::NeitherFeatureNorEnvVar =>  write!(f, "Called a method requiring env var `BITCOIND_EXE` or a feature to be set, but neither are set"),
+            Error::NoBitcoindExecutableFound =>  write!(f, "`bitcoind` executable is required, provide it with one of the following: set env var `BITCOIND_EXE` or use a feature like \"22_0\" or have `bitcoind` executable in the `PATH`"),
             Error::BothFeatureAndEnvVar => write!(f, "Called a method requiring env var `BITCOIND_EXE` or a feature to be set, but both are set"),
             Error::EarlyExit(e) => write!(f, "The bitcoind process terminated early with exit code {}", e),
             Error::BothDirsSpecified => write!(f, "tempdir and staticdir cannot be enabled at same time in configuration options")
@@ -417,7 +418,9 @@ pub fn exe_path() -> Result<String, Error> {
         (Ok(_), Ok(_)) => Err(Error::BothFeatureAndEnvVar),
         (Ok(path), Err(_)) => Ok(path),
         (Err(_), Ok(path)) => Ok(path),
-        (Err(_), Err(_)) => Err(Error::NeitherFeatureNorEnvVar),
+        (Err(_), Err(_)) => which::which("bitcoind")
+            .map_err(|_| Error::NoBitcoindExecutableFound)
+            .map(|p| p.display().to_string()),
     }
 }