Add test for json output

This also fixes a few bugs in jsondocck and makes some of its errors easier to read.

Author: jyn514

src/rustdoc-json-types/lib.rs

@@ -69,6 +69,10 @@ pub struct Item {
     /// so this field is needed to differentiate.
     pub visibility: Visibility,
     /// The full markdown docstring of this item.
+    ///
+    /// This field has already been pre-parsed, including combining lines and de-indenting
+    /// whitespace. Each line is delimited by a newline, but the docs will not end with a trailing
+    /// newline (unless added explicitly by the user with `#[doc = "\n"]`).
     pub docs: String,
     /// This mapping resolves [intra-doc links](https://github.com/rust-lang/rfcs/blob/master/text/1946-intra-rustdoc-links.md) from the docstring to their IDs
     pub links: HashMap<String, Id>,

src/test/rustdoc-json/empty-lines.rs

@@ -0,0 +1,12 @@
+// @has empty_lines.json "$.index[*][?(@.name == 'foo')]"
+// @has - "$.index[*][?(@.name == 'foo')].docs" \"\\n\\n\"
+///
+///
+///
+// ^ note that the above line does *not* include a trailing new line in the docs
+pub fn foo() {}
+
+// @has empty_lines.json "$.index[*][?(@.name == 'bar')].docs" "\"first line\\nsecond line \""
+#[doc = "\n first line"]
+#[doc = "\n second line \n"]
+pub fn bar() {}

src/tools/compiletest/src/runtest.rs

@@ -2401,8 +2401,6 @@ impl<'test> TestCx<'test> {
         }
 
         let root = self.config.find_rust_src_root().unwrap();
-        let mut json_out = out_dir.join(self.testpaths.file.file_stem().unwrap());
-        json_out.set_extension("json");
         let res = self.cmd2procres(
             Command::new(self.config.jsondocck_path.as_ref().unwrap())
                 .arg("--doc-dir")
@@ -2415,7 +2413,9 @@ impl<'test> TestCx<'test> {
             self.fatal_proc_rec("jsondocck failed!", &res)
         }
 
-        let mut json_out = out_dir.join(self.testpaths.file.file_stem().unwrap());
+        let crate_name =
+            self.testpaths.file.file_stem().unwrap().to_str().unwrap().replace('-', "_");
+        let mut json_out = out_dir.join(crate_name);
         json_out.set_extension("json");
         let res = self.cmd2procres(
             Command::new(&self.config.docck_python)

src/tools/jsondocck/src/main.rs

@@ -62,7 +62,10 @@ impl CommandKind {
         };
 
         if !count {
-            print_err(&format!("Incorrect number of arguments to `@{}`", self), lineno);
+            print_err(
+                &format!("Incorrect number of arguments to `@{}` (got {})", self, args.len()),
+                lineno,
+            );
             return false;
         }
 
@@ -317,6 +320,8 @@ fn string_to_value<'a>(s: &str, cache: &'a Cache) -> Cow<'a, Value> {
             panic!("No variable: `{}`. Current state: `{:?}`", &s[1..], cache.variables)
         }))
     } else {
-        Cow::Owned(serde_json::from_str(s).unwrap())
+        Cow::Owned(serde_json::from_str(s).unwrap_or_else(|err| {
+            panic!("failed to parse {:?} as a string: {}", s, err);
+        }))
     }
 }