add tests for rustdoc output-format json

Author: GuillaumeGomez

src/test/rustdoc-ui/coverage/json.rs

@@ -0,0 +1,27 @@
+// build-pass
+// compile-flags:-Z unstable-options --show-coverage
+
+pub mod foo {
+    /// Hello!
+    pub struct Foo;
+    /// Bar
+    pub enum Bar { A }
+}
+
+/// X
+pub struct X;
+
+/// Bar
+pub mod bar {
+    /// bar
+    pub struct Bar;
+    /// X
+    pub enum X { Y }
+}
+
+/// yolo
+pub enum Yolo { X }
+
+pub struct Xo<T: Clone> {
+    x: T,
+}

src/test/rustdoc-ui/coverage/json.stdout

@@ -0,0 +1,7 @@
++-------------------------------------+------------+------------+------------+
+| File                                | Documented |      Total | Percentage |
++-------------------------------------+------------+------------+------------+
+| ...test/rustdoc-ui/coverage/json.rs |          7 |         13 |      53.8% |
++-------------------------------------+------------+------------+------------+
+| Total                               |          7 |         13 |      53.8% |
++-------------------------------------+------------+------------+------------+

src/test/rustdoc/output-format-fail-check.rs

@@ -0,0 +1,5 @@
+// compile-flags:-Z unstable-options --output-format
+// should-fail
+
+/// toudoum!
+pub struct SomeStruct;