Refactor to use cargo metadata instead of cargo read-manifest (deprec…

…ated)

This also gives us some workspace support (you need to choose a target from workspace)
Improves #8 but only by not crashing on workspaces. We still show one target.

The current assumption of one lib max fails when running in a workspace.
Since the current code does not allow to select a specific lib target

Also there are more target kinds than bin and lib that might be interesting to parse.

We should revist the user experience here or always show the whole workspace.

src/main.rs

@@ -38,36 +38,25 @@ use dot_printer::DotPrinter;
 fn choose_target<'a>(args: &Arguments, manifest: &'a Manifest) -> Result<&'a Target, Error> {
     if args.lib {
         // If `--lib` is enabled use the first library target.
-        manifest
-            .targets
-            .iter()
-            .find(|t| t.is_lib())
-            .ok_or(Error::NoLibraryTargetFound)
+        manifest.lib()
     } else if let Some(ref name) = args.bin {
         // If a binary target is specified use that.
-        manifest
-            .targets
-            .iter()
-            .find(|t| t.is_bin() && t.name() == name)
-            .ok_or(Error::NoMatchingBinaryTargetFound)
-    } else if manifest.targets.len() == 1 {
+        manifest.bin(name)
+    } else if manifest.targets().len() == 1 {
         // If neither `--lib` is enabled nor `--bin` target is specified but
         // there is only one target, use that.
-        Ok(manifest.targets.first().unwrap())
+        Ok(manifest.targets().first().unwrap())
     } else {
         // If there are multiple targets use the first library target.
-        manifest
-            .targets
-            .iter()
-            .find(|t| t.is_lib())
-            .ok_or(Error::NoTargetProvided)
+        manifest.lib().or(Err(Error::NoTargetProvided))
     }
 }
 
 fn run(args: &Arguments) -> Result<(), Error> {
     let manifest: Manifest = {
         let output = process::Command::new("cargo")
-            .arg("read-manifest")
+            .arg("metadata")
+            .args(&["--no-deps", "--format-version", "1"])
             .output()
             .map_err(Error::CargoExecutionFailed)?;
         let stdout = output.stdout;
@@ -78,14 +67,6 @@ fn run(args: &Arguments) -> Result<(), Error> {
         Manifest::from_str(&json_string)?
     };
 
-    if args.enable_edition_2018 && manifest.edition == Edition::E2018 {
-        println!(
-            "{}\n{}",
-            "Edition 2018 support is work in progress.".red(),
-            "`--enable-edition-2018` will be ignored.".red()
-        );
-    }
-
     // TODO: Check to see if build scripts really need to be ignored.
     //       Seems like they are not mistaken as orphans anyway.
     let build_scripts: Vec<path::PathBuf> = manifest
@@ -95,6 +76,15 @@ fn run(args: &Arguments) -> Result<(), Error> {
         .collect();
 
     let target: &Target = choose_target(args, &manifest)?;
+
+    if args.enable_edition_2018 && target.edition == Edition::E2018 {
+        println!(
+            "{}\n{}",
+            "Edition 2018 support is work in progress.".red(),
+            "`--enable-edition-2018` will be ignored.".red()
+        );
+    }
+
     let parse_session = ParseSess::new(source_map::FilePathMapping::empty());
 
     syntax::with_globals(|| {