pipeline: accept boxed trait objects

It's kinda silly to have new() be generic when all it does is box the
objects anyway. It only makes code harder to write, as we cannot unify
the types to call Pipeline::new(), and instead we have to rely on
calling Pipeline::new() in the branches themselves.

It's not the biggest issue when we only have different formats, but at
some point we might want to add different aggregators as well (like a
sorting one or a counting one), so it would be bad if we suddenly had to
add all those branches.

This fix changes that, and we can build the pipeline piecewise by
having a Box<dyn Format> around, allowing us to combine it freely with
any Box<dyn Aggregator>.

1 files changed, 8 insertions, 6 deletions

diff --git a/src/output/mod.rs b/src/output/mod.rs
index 84ed0a4..aadcbf9 100644
--- a/src/output/mod.rs
+++ b/src/output/mod.rs
@@ -8,18 +8,20 @@ pub mod pipeline;
 
 pub use self::pipeline::Pipeline;
 
+use self::formats::Format;
 
 /// Build an pipeline for the given command line options.
 pub fn build_pipeline(opt: &Opt) -> Pipeline {
     let stream = io::stdout();
     let aggregator = aggregators::WriteThrough;
 
-    if opt.file_name_only {
-        Pipeline::new(stream, formats::FileOnly, aggregator)
+    let format: Box<dyn Format> = if opt.file_name_only {
+        Box::new(formats::FileOnly)
     } else {
-        let format = formats::HumanReadable {
+        Box::new(formats::HumanReadable {
             show_guilds: opt.guilds,
-        };
-        Pipeline::new(stream, format, aggregator)
-    }
+        })
+    };
+
+    Pipeline::new(Box::new(stream), format, Box::new(aggregator))
 }