Add logging support & some preliminary logging

This is just generally nice to have, and is already a transitive
dependency, so let's go ahead.

Cargo.toml

@@ -21,3 +21,5 @@ chrono = "0.4.6"
 structopt = { version = "^0.3", default-features = false }
 semver = "1.0"
 termcolor = "1.0"
+env_logger = "0.10.0"
+log = "0.4.20"

src/app.rs

@@ -18,6 +18,7 @@ use crate::opt::{AppConfig, CargoOpts, Target};
 pub(crate) fn run(app_config: AppConfig) -> Result<()> {
     // 1. Detect the type of Xcode Instruments installation
     let xctrace_tool = instruments::XcodeInstruments::detect()?;
+    log::debug!("using {xctrace_tool}");
 
     // 2. Render available templates if the user asked
     if app_config.list_templates {
@@ -35,6 +36,8 @@ pub(crate) fn run(app_config: AppConfig) -> Result<()> {
         None => important_paths::find_root_manifest_for_wd(cargo_config.cwd()),
     }?;
 
+    log::debug!("using cargo manifest at {}", manifest_path.display());
+
     let workspace = Workspace::new(&manifest_path, &cargo_config)?;
 
     // 3.1: warn if --open passed. We do this here so we have access to cargo's
@@ -48,6 +51,8 @@ pub(crate) fn run(app_config: AppConfig) -> Result<()> {
     }
 
     let cargo_options = app_config.to_cargo_opts()?;
+
+    log::debug!("building profile target {}", cargo_options.target);
     let target_filepath = match build_target(&cargo_options, &workspace) {
         Ok(path) => path,
         Err(e) => {
@@ -56,6 +61,8 @@ pub(crate) fn run(app_config: AppConfig) -> Result<()> {
         }
     };
 
+    log::debug!("running against target {}", target_filepath.display());
+
     #[cfg(target_arch = "aarch64")]
     codesign(&target_filepath, &workspace)?;
 
@@ -176,7 +183,7 @@ fn make_compile_opts(cargo_options: &CargoOpts, cfg: &Config) -> Result<CompileO
     compile_options.cli_features = cargo_options.features.clone();
     compile_options.spec = cargo_options.package.clone().into();
 
-    if cargo_options.target != Target::Main {
+    if cargo_options.target != Target::Default {
         let (bins, examples, benches) = match &cargo_options.target {
             Target::Bin(bin) => (vec![bin.clone()], vec![], vec![]),
             Target::Example(bin) => (vec![], vec![bin.clone()], vec![]),

src/instruments.rs

@@ -1,6 +1,6 @@
 //! interfacing with the `instruments` command line tool
 
-use std::fmt::Write;
+use std::fmt::{Display, Write};
 use std::fs;
 use std::path::{Path, PathBuf};
 use std::process::{Command, Output};
@@ -485,6 +485,15 @@ fn get_tty() -> Result<Option<String>> {
         .map(|tty| format!("/dev/{}", tty)))
 }
 
+impl Display for XcodeInstruments {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            XcodeInstruments::XcTrace => f.write_str("xctrace"),
+            XcodeInstruments::InstrumentsBinary => f.write_str("legacy instruments binary"),
+        }
+    }
+}
+
 #[cfg(test)]
 mod test {
     use super::*;

src/main.rs

@@ -6,6 +6,7 @@ mod opt;
 compile_error!("cargo-instruments requires macOS.");
 
 fn main() {
+    env_logger::init();
     use structopt::StructOpt;
     let opt::Cli::Instruments(args) = opt::Cli::from_args();
 

src/opt.rs

@@ -115,7 +115,7 @@ pub(crate) struct AppConfig {
 /// Represents the kind of target to profile.
 #[derive(Debug, PartialEq)]
 pub(crate) enum Target {
-    Main,
+    Default,
     Example(String),
     Bin(String),
     Bench(String),
@@ -151,10 +151,10 @@ impl fmt::Display for Package {
 impl fmt::Display for Target {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         match self {
-            Target::Main => write!(f, "src/main.rs"),
-            Target::Example(bin) => write!(f, "examples/{}.rs", bin),
-            Target::Bin(bin) => write!(f, "bin/{}.rs", bin),
-            Target::Bench(bench) => write!(f, "bench {}", bench),
+            Target::Default => write!(f, "default"),
+            Target::Example(bin) => write!(f, "{bin} (example)",),
+            Target::Bin(bin) => write!(f, "{bin} (bin)"),
+            Target::Bench(bench) => write!(f, "{bench} (bench)"),
         }
     }
 }
@@ -201,7 +201,7 @@ impl AppConfig {
         } else if let Some(ref bench) = self.bench {
             Target::Bench(bench.clone())
         } else {
-            Target::Main
+            Target::Default
         }
     }
 }