Auto merge of #587 - fitzgen:little-helper-stuff, r=emilio

Little helper stuff

A couple things that I've found helpful for iterative debugging.

r? @emilio

Author: bors-servo

CONTRIBUTING.md

@@ -94,6 +94,17 @@ Run `cargo test` to compare generated Rust bindings to the expectations.
 $ cargo test [--all-features]
 ```
 
+### Running a Single Test
+
+To generate bindings for a single test header, compile the bindings, and run the
+layout assertion tests for those bindings, use the `tests/test-one.sh`
+script. It supports fuzzy searching for test headers. For example, to test
+`tests/headers/what_is_going_on.hpp`, execute this command:
+
+```
+$ ./tests/test-one.sh going
+```
+
 ### Authoring New Tests
 
 To add a new test header to the suite, simply put it in the `tests/headers`

src/ir/dot.rs

@@ -36,15 +36,16 @@ pub fn write_dot_file<P>(ctx: &BindgenContext, path: P) -> io::Result<()>
         try!(writeln!(&mut dot_file, r#"</table> >];"#));
 
         item.trace(ctx,
-                   &mut |sub_id: ItemId, _edge_kind| {
+                   &mut |sub_id: ItemId, edge_kind| {
             if err.is_some() {
                 return;
             }
 
             match writeln!(&mut dot_file,
-                           "{} -> {};",
+                           "{} -> {} [label={:?}];",
                            id.as_usize(),
-                           sub_id.as_usize()) {
+                           sub_id.as_usize(),
+                           edge_kind) {
                 Ok(_) => {}
                 Err(e) => err = Some(Err(e)),
             }

tests/test-one.sh

@@ -0,0 +1,36 @@
+#!/usr/bin/env bash
+
+# Usage:
+#
+#     ./tests/test-one.sh <fuzzy-name>
+#
+# Generate bindings for the first match of `./tests/headers/*<fuzzy-name>*`, use
+# `rustc` to compile the bindings with unit tests enabled, and run the generated
+# layout tests.
+
+set -eux
+
+cd $(dirname $0)
+cd ..
+
+export RUST_BACKTRACE=1
+
+# Grab the first match
+TEST=$(find ./tests/headers -type f -iname "*$1*" | head -n 1)
+
+BINDINGS=$(mktemp -t bindings_XXXXXX.rs)
+TEST_BINDINGS_BINARY=$(mktemp -t bindings.XXXXX)
+
+./target/debug/bindgen \
+    "$TEST" \
+    --emit-ir \
+    --emit-ir-graphviz ir.dot \
+    --emit-clang-ast \
+    -o "$BINDINGS" \
+    -- -std=c++14
+
+dot -Tpng ir.dot -o ir.png
+
+rustc --test -o "$TEST_BINDINGS_BINARY" "$BINDINGS"
+
+"$TEST_BINDINGS_BINARY"