Update test harness for browser testing

This commit updates the test harness for in-browser testing. It now no longer
unconditionally uses `fs.writeSync`, for example. Instead a `Formatter` trait is
introduced for both Node/browser environments and at runtime we detect which is
the appropriate one to use.

crates/test/src/lib.rs

@@ -20,6 +20,6 @@ macro_rules! console_log {
     )
 }
 
-#[path = "rt.rs"]
+#[path = "rt/mod.rs"]
 #[doc(hidden)]
 pub mod __rt;

crates/test/src/rt/browser.rs

@@ -0,0 +1,111 @@
+//! Support for printing status information of a test suite in a browser.
+//!
+//! Currently this is quite simple, rendering the same as the console tests in
+//! node.js. Output here is rendered in a `pre`, however.
+
+use wasm_bindgen::prelude::*;
+use js_sys::Error;
+
+pub struct Browser {
+    pre: Element,
+}
+
+#[wasm_bindgen]
+extern {
+    type HTMLDocument;
+    static document: HTMLDocument;
+    #[wasm_bindgen(method, structural)]
+    fn getElementById(this: &HTMLDocument, id: &str) -> Element;
+
+    type Element;
+    #[wasm_bindgen(method, getter = innerHTML, structural)]
+    fn inner_html(this: &Element) -> String;
+    #[wasm_bindgen(method, setter = innerHTML, structural)]
+    fn set_inner_html(this: &Element, html: &str);
+
+    type BrowserError;
+    #[wasm_bindgen(method, getter, structural)]
+    fn stack(this: &BrowserError) -> JsValue;
+}
+
+impl Browser {
+    pub fn new() -> Browser {
+        let pre = document.getElementById("output");
+        pre.set_inner_html("");
+        Browser {
+            pre,
+        }
+    }
+}
+
+impl super::Formatter for Browser {
+    fn writeln(&self, line: &str) {
+        let mut html = self.pre.inner_html();
+        html.push_str(&line);
+        html.push_str("\n");
+        self.pre.set_inner_html(&html);
+    }
+
+    fn log_start(&self, name: &str) {
+        let data = format!("test {} ... ", name);
+        let mut html = self.pre.inner_html();
+        html.push_str(&data);
+        self.pre.set_inner_html(&html);
+    }
+
+    fn log_success(&self) {
+        let mut html = self.pre.inner_html();
+        html.push_str("ok\n");
+        self.pre.set_inner_html(&html);
+    }
+
+    fn log_ignored(&self) {
+        let mut html = self.pre.inner_html();
+        html.push_str("ignored\n");
+        self.pre.set_inner_html(&html);
+    }
+
+    fn log_failure(&self, err: JsValue) -> String {
+        let mut html = self.pre.inner_html();
+        html.push_str("FAIL\n");
+        self.pre.set_inner_html(&html);
+
+        // TODO: this should be a checked cast to `Error`
+        let err = Error::from(err);
+        let name = String::from(err.name());
+        let message = String::from(err.message());
+        let err = BrowserError::from(JsValue::from(err));
+        let stack = err.stack();
+
+        let mut header = format!("{}: {}", name, message);
+        let stack = match stack.as_string() {
+            Some(stack) => stack,
+            None => return header,
+        };
+
+        // If the `stack` variable contains the name/message already, this is
+        // probably a chome-like error which is already rendered well, so just
+        // return this info
+        if stack.contains(&header) {
+            return stack
+        }
+
+        // Check for a firefox-like error where all lines have a `@` in them
+        // separating the symbol and source
+        if stack.lines().all(|s| s.contains("@")) {
+            for line in stack.lines() {
+                header.push_str("\n");
+                header.push_str("  at");
+                for part in line.split("@") {
+                    header.push_str(" ");
+                    header.push_str(part);
+                }
+            }
+            return header
+        }
+
+        // Fallback to make sure we don't lose any info
+        format!("{}\n{}", header, stack)
+    }
+}
+

crates/test/src/rt/detect.rs

@@ -0,0 +1,62 @@
+use wasm_bindgen::prelude::*;
+use js_sys::{Array, Function};
+
+#[wasm_bindgen]
+extern {
+    #[wasm_bindgen(js_name = Function)]
+    fn new_function(s: &str) -> Function;
+
+    type This;
+    #[wasm_bindgen(method, getter, structural, js_name = self)]
+    fn self_(me: &This) -> JsValue;
+}
+
+/// Returns whether it's likely we're executing in a browser environment, as
+/// opposed to node.js.
+pub fn is_browser() -> bool {
+    // This is a bit tricky to define. The basic crux of this is that we want to
+    // test if the `self` identifier is defined. That is defined in browsers
+    // (and web workers!) but not in Node. To that end you might expect:
+    //
+    //      #[wasm_bindgen]
+    //      extern {
+    //          #[wasm_bindgen(js_name = self)]
+    //          static SELF: JsValue;
+    //      }
+    //
+    //      *SELF != JsValue::undefined()
+    //
+    // this currently, however, throws a "not defined" error in JS because the
+    // generated function looks like `function() { return self; }` which throws
+    // an error in Node because `self` isn't defined.
+    //
+    // To work around this limitation we instead lookup the value of `self`
+    // through the `this` object, basically generating `this.self`.
+    //
+    // Unfortunately that's also hard to do! In ESM modes the top-level `this`
+    // object is undefined, meaning that we can't just generate a function that
+    // returns `this.self` as it'll throw "can't access field `self` of
+    // `undefined`" whenever ESMs are being used.
+    //
+    // So finally we reach the current implementation. According to
+    // StackOverflow you can access the global object via:
+    //
+    //      const global = Function('return this')();
+    //
+    // I think that's because the manufactured function isn't in "strict" mode.
+    // It also turns out that non-strict functions will ignore `undefined`
+    // values for `this` when using the `apply` function. Add it all up, and you
+    // get the below code:
+    //
+    // * Manufacture a function
+    // * Call `apply` where we specify `this` but the function ignores it
+    // * Once we have `this`, use a structural getter to get the value of `self`
+    // * Last but not least, test whether `self` is defined or not.
+    //
+    // Whew!
+    let this = new_function("return this")
+        .apply(&JsValue::undefined(), &Array::new())
+        .unwrap();
+    assert!(this != JsValue::undefined());
+    This::from(this).self_() != JsValue::undefined()
+}

crates/test/src/rt/mod.rs

@@ -1,3 +1,5 @@
+#![doc(hidden)]
+
 use std::cell::{RefCell, Cell};
 use std::fmt;
 use std::mem;
@@ -6,6 +8,10 @@ use console_error_panic_hook;
 use js_sys::{Array, Function};
 use wasm_bindgen::prelude::*;
 
+pub mod node;
+pub mod browser;
+pub mod detect;
+
 /// Runtime test harness support instantiated in JS.
 ///
 /// The node.js entry script instantiates a `Context` here which is used to
@@ -20,6 +26,15 @@ pub struct Context {
     current_log: RefCell<String>,
     current_error: RefCell<String>,
     ignore_this_test: Cell<bool>,
+    formatter: Box<Formatter>,
+}
+
+trait Formatter {
+    fn writeln(&self, line: &str);
+    fn log_start(&self, name: &str);
+    fn log_success(&self);
+    fn log_ignored(&self);
+    fn log_failure(&self, err: JsValue) -> String;
 }
 
 #[wasm_bindgen]
@@ -28,32 +43,26 @@ extern {
     #[doc(hidden)]
     pub fn console_log(s: &str);
 
-    // Not using `js_sys::Error` because node's errors specifically have a
-    // `stack` attribute.
-    type NodeError;
-    #[wasm_bindgen(method, getter, js_class = "Error", structural)]
-    fn stack(this: &NodeError) -> String;
-
     // General-purpose conversion into a `String`.
     #[wasm_bindgen(js_name = String)]
     fn stringify(val: &JsValue) -> String;
 }
 
-#[wasm_bindgen(module = "fs", version = "*")]
-extern {
-    fn writeSync(fd: i32, data: &[u8]);
-}
-
 pub fn log(args: &fmt::Arguments) {
     console_log(&args.to_string());
 }
 
 #[wasm_bindgen]
+
 impl Context {
     #[wasm_bindgen(constructor)]
     pub fn new() -> Context {
         console_error_panic_hook::set_once();
 
+        let formatter = match node::Node::new() {
+            Some(node) => Box::new(node) as Box<Formatter>,
+            None => Box::new(browser::Browser::new()),
+        };
         Context {
             filter: None,
             current_test: RefCell::new(None),
@@ -63,6 +72,7 @@ impl Context {
             current_log: RefCell::new(String::new()),
             current_error: RefCell::new(String::new()),
             ignore_this_test: Cell::new(false),
+            formatter,
         }
     }
 
@@ -95,8 +105,8 @@ impl Context {
         args.push(&JsValue::from(self as *const Context as u32));
 
         let noun = if tests.len() == 1 { "test" } else { "tests" };
-        console_log!("running {} {}", tests.len(), noun);
+        self.formatter.writeln(&format!("running {} {}", tests.len(), noun));
-        console_log!("");
+        self.formatter.writeln("");
 
         for test in tests {
             self.ignore_this_test.set(false);
@@ -109,7 +119,7 @@ impl Context {
                         self.log_success()
                     }
                 }
-                Err(e) => self.log_error(e.into()),
+                Err(e) => self.log_failure(e),
             }
             drop(self.current_test.borrow_mut().take());
             *self.current_log.borrow_mut() = String::new();
@@ -123,22 +133,20 @@ impl Context {
         let mut current_test = self.current_test.borrow_mut();
         assert!(current_test.is_none());
         *current_test = Some(test.to_string());
-        let data = format!("test {} ... ", test);
+        self.formatter.log_start(test);
-        writeSync(2, data.as_bytes());
     }
 
     fn log_success(&self) {
-        writeSync(2, b"ok\n");
+        self.formatter.log_success();
         self.succeeded.set(self.succeeded.get() + 1);
     }
 
     fn log_ignore(&self) {
-        writeSync(2, b"ignored\n");
+        self.formatter.log_ignored();
         self.ignored.set(self.ignored.get() + 1);
     }
 
-    fn log_error(&self, err: NodeError) {
+    fn log_failure(&self, err: JsValue) {
-        writeSync(2, b"FAILED\n");
         let name = self.current_test.borrow().as_ref().unwrap().clone();
         let log = mem::replace(&mut *self.current_log.borrow_mut(), String::new());
         let error = mem::replace(&mut *self.current_error.borrow_mut(), String::new());
@@ -154,25 +162,25 @@ impl Context {
             msg.push_str("\n");
         }
         msg.push_str("JS exception that was thrown:\n");
-        msg.push_str(&tab(&err.stack()));
+        msg.push_str(&tab(&self.formatter.log_failure(err)));
         self.failures.borrow_mut().push((name, msg));
     }
 
     fn log_results(&self) {
         let failures = self.failures.borrow();
         if failures.len() > 0 {
-            console_log!("\nfailures:\n");
+            self.formatter.writeln("\nfailures:\n");
             for (test, logs) in failures.iter() {
-                console_log!("---- {} output ----\n{}\n", test, tab(logs));
+                let msg = format!("---- {} output ----\n{}", test, tab(logs));
+                self.formatter.writeln(&msg);
             }
-            console_log!("failures:\n");
+            self.formatter.writeln("failures:\n");
             for (test, _) in failures.iter() {
-                console_log!("    {}\n", test);
+                self.formatter.writeln(&format!("    {}", test));
             }
-        } else {
-            console_log!("");
         }
-        console_log!(
+        self.formatter.writeln("");
+        self.formatter.writeln(&format!(
             "test result: {}. \
              {} passed; \
              {} failed; \
@@ -181,7 +189,7 @@ impl Context {
             self.succeeded.get(),
             failures.len(),
             self.ignored.get(),
-        );
+        ));
     }
 
     pub fn console_log(&self, original: &Function, args: &Array) {

crates/test/src/rt/node.rs

@@ -0,0 +1,60 @@
+//! Support for printing status information of a test suite in node.js
+//!
+//! This currently uses the same output as `libtest`, only reimplemented here
+//! for node itself.
+
+use wasm_bindgen::prelude::*;
+use js_sys::eval;
+
+pub struct Node {
+    fs: NodeFs,
+}
+
+#[wasm_bindgen]
+extern {
+    type NodeFs;
+    #[wasm_bindgen(method, js_name = writeSync, structural)]
+    fn write_sync(this: &NodeFs, fd: i32, data: &[u8]);
+
+    // Not using `js_sys::Error` because node's errors specifically have a
+    // `stack` attribute.
+    type NodeError;
+    #[wasm_bindgen(method, getter, js_class = "Error", structural)]
+    fn stack(this: &NodeError) -> String;
+}
+
+impl Node {
+    pub fn new() -> Option<Node> {
+        if super::detect::is_browser() {
+            return None
+        }
+
+        let import = eval("require(\"fs\")").unwrap();
+        Some(Node { fs: import.into() })
+    }
+}
+
+impl super::Formatter for Node {
+    fn writeln(&self, line: &str) {
+        super::console_log(line);
+    }
+
+    fn log_start(&self, name: &str) {
+        let data = format!("test {} ... ", name);
+        self.fs.write_sync(2, data.as_bytes());
+    }
+
+    fn log_success(&self) {
+        self.fs.write_sync(2, b"ok\n");
+    }
+
+    fn log_ignored(&self) {
+        self.fs.write_sync(2, b"ignored\n");
+    }
+
+    fn log_failure(&self, err: JsValue) -> String {
+        self.fs.write_sync(2, b"ignored\n");
+        // TODO: should do a checked cast to `NodeError`
+        NodeError::from(err).stack()
+    }
+}