feat: Tree view of Predicate result (Case)

Finnaly, Fixes assert-rs#7.

Inspired by the work in assert-rs#39.

Created softprops/treeline#3 for trying to find ways to make this more
efficient.

Cargo.toml

@@ -21,7 +21,9 @@ appveyor = { repository = "assert-rs/predicates-rs" }
 difference = { version = "2.0", optional = true }
 regex = { version="1.0", optional = true }
 float-cmp = { version="0.4", optional = true }
+treeline = { version = "0.1", optional = true }
 
 [features]
-default = ["difference", "regex", "float-cmp"]
+default = ["difference", "regex", "float-cmp", "tree"]
 unstable = []
+tree = ["treeline",]

examples/case_tree.rs

@@ -0,0 +1,15 @@
+extern crate predicates;
+
+use predicates::prelude::*;
+use predicates::tree::CaseTreeExt;
+
+fn main() {
+    let pred = predicate::ne(5).not().and(predicate::ge(5));
+
+    let var = 5;
+    let case = pred.find_case(true, &var);
+    if let Some(case) = case {
+        println!("var is {}", var);
+        println!("{}", case.tree());
+    }
+}

src/lib.rs

@@ -98,6 +98,8 @@ extern crate difference;
 extern crate float_cmp;
 #[cfg(feature = "regex")]
 extern crate regex;
+#[cfg(feature = "treeline")]
+extern crate treeline;
 
 pub mod prelude;
 
@@ -121,3 +123,5 @@ pub mod boolean;
 pub mod float;
 pub mod path;
 pub mod str;
+#[cfg(feature = "tree")]
+pub mod tree;

src/tree.rs

@@ -0,0 +1,60 @@
+// Copyright (c) 2018 The predicates-rs Project Developers.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/license/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! Render `Case` as a tree.
+
+use std::fmt;
+
+use treeline;
+
+use reflection;
+
+/// Render `Self` as a displayable tree.
+pub trait CaseTreeExt {
+    /// Render `Self` as a displayable tree.
+    fn tree(&self) -> CaseTree;
+}
+
+impl<'a> CaseTreeExt for reflection::Case<'a> {
+    fn tree(&self) -> CaseTree {
+        CaseTree(convert(self))
+    }
+}
+
+type CaseTreeInner = treeline::Tree<Box<fmt::Display>>;
+
+fn convert<'a>(case: &reflection::Case<'a>) -> CaseTreeInner {
+    let mut leaves: Vec<CaseTreeInner> = vec![];
+
+    leaves.extend(case.predicate().iter().flat_map(|pred| {
+        pred.parameters().map(|item| {
+            let root: Box<fmt::Display> = Box::new(item.to_string());
+            treeline::Tree::new(root, vec![])
+        })
+    }));
+
+    leaves.extend(case.products().map(|item| {
+        let root: Box<fmt::Display> = Box::new(item.to_string());
+        treeline::Tree::new(root, vec![])
+    }));
+
+    leaves.extend(case.children().map(|item| convert(item)));
+
+    let root = Box::new(case.predicate().map(|p| p.to_string()).unwrap_or_default());
+    CaseTreeInner::new(root, leaves)
+}
+
+/// A `Case` rendered as a tree for display.
+#[allow(missing_debug_implementations)]
+pub struct CaseTree(CaseTreeInner);
+
+impl fmt::Display for CaseTree {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        self.0.fmt(f)
+    }
+}