Check for duplicate library names

lib/runtime/dart_runtime.js

Index: lib/runtime/dart_runtime.js
diff --git a/lib/runtime/dart_runtime.js b/lib/runtime/dart_runtime.js
index 200d187f7e01a6436d27ab56f7eb53e6aa172304..6683bc9768f592cd7a23fdb418d30fcae633d72c 100644
--- a/lib/runtime/dart_runtime.js
+++ b/lib/runtime/dart_runtime.js
@@ -50,6 +50,11 @@ var dart, _js_helper, _js_primitives;
   }
   dart.dput = dput;
 
+  function throwRuntimeError(message) {
+    console.error(message);

[Jennifer Messerly, 2015/06/05 16:22:27]

what's the benefit of logging and throwing? Don't they both appear at the
console?

[vsm, 2015/06/05 17:01:04]

removed

+    throw new _js_helper.RuntimeError(message);

[Jennifer Messerly, 2015/06/05 16:22:27]

what happens if this isn't loaded? don't we have bootstrapping issues?
it seems better to just throw a JS Error. I suspect this will all be replaced
with a general module loader pattern/polyfill at some point, so it won't even be
Dart specific.

[vsm, 2015/06/05 17:01:04]

Done.

+  }
+
   // TODO(jmesserly): this should call noSuchMethod, not throw.
   function throwNoSuchMethod(obj, name, args, opt_func) {
     if (obj === void 0) obj = opt_func;
@@ -431,15 +436,15 @@ var dart, _js_helper, _js_primitives;
 
   /** Checks that `x` is not null or undefined. */
   function notNull(x) {
-    if (x == null) throw 'expected not-null value';
+    if (x == null) throwRuntimeError('expected not-null value');
     return x;
   }
   dart.notNull = notNull;
 
   function _typeName(type) {
-    if (type === void 0) throw "Undefined type";
+    if (type === void 0) throwRuntimeError('Undefined type');
     var name = type.name;
-    if (!name) throw 'Unexpected type: ' + type;
+    if (!name) throwRuntimeError('Unexpected type: ' + type);
     return name;
   }
 
@@ -727,7 +732,7 @@ var dart, _js_helper, _js_primitives;
     function lazyGetter() {
       // Clear the init function to detect circular initialization.
       let f = init;
-      if (f === null) throw 'circular initialization for field ' + name;
+      if (f === null) throwRuntimeError('circular initialization for field ' + name);
       init = null;
 
       // Compute and store the value.
@@ -906,8 +911,7 @@ var dart, _js_helper, _js_primitives;
   dart.map = map;
 
   function assert(condition) {
-    // TODO(jmesserly): throw assertion error.
-    if (!condition) throw 'assertion failed';
+    if (!condition) throw new core.AssertionError();
   }
   dart.assert = assert;
 
@@ -941,12 +945,12 @@ var dart, _js_helper, _js_primitives;
   /** Memoize a generic type constructor function. */
   function generic(typeConstructor) {
     let length = typeConstructor.length;
-    if (length < 1) throw Error('must have at least one generic type argument');
+    if (length < 1) throwRuntimeError('must have at least one generic type argument');
 
     let resultMap = new Map();
     function makeGenericType(/*...arguments*/) {
       if (arguments.length != length && arguments.length != 0) {
-        throw Error('requires ' + length + ' or 0 type arguments');
+        throwRuntimeError('requires ' + length + ' or 0 type arguments');
       }
       let args = Array.prototype.slice.call(arguments);
       // TODO(leafp): This should really be core.Object for
@@ -959,7 +963,7 @@ var dart, _js_helper, _js_primitives;
       for (let i = 0; i < length; i++) {
         let arg = args[i];
         if (arg == null) {
-          throw Error('type arguments should not be null: ' + typeConstructor);
+          throwRuntimeError('type arguments should not be null: ' + typeConstructor);
         }
         let map = value;
         value = map.get(arg);
@@ -1230,24 +1234,51 @@ var dart, _js_helper, _js_primitives;
   dart.global = window || global;
   dart.JsSymbol = Symbol;
 
-  function import_(value) {
+  var loadedLibraries = {};

[Jennifer Messerly, 2015/06/05 16:22:27]

How will this work with JS interop? It seems we are assuming closed world here,
in other words, that all modules come from Dart. I was hoping we could integrate
more naturally at runtime with the JS code that's been loaded

[vsm, 2015/06/05 17:01:04]

Not really assuming a closed world.  For JS code, we can either:
(1) Always use lazyImport - we never require a lib to be in loadedLibraries to
run code
(2) Provide a different import / register API
(3) Make import a little more forgiving - though it *is* catching real errors
right now

+
+  function import_(name) {
+    let value = loadedLibraries[name];
     // TODO(vsm): Change this to a hard throw.
     // For now, we're missing some libraries.  E.g., dart:js:
     // https://github.com/dart-lang/dev_compiler/issues/168
     if (!value) {
-      console.log('missing required module');
+      console.warn('Missing required module: ' + name);
+    } else if (value != dart.global[name]) {
+      throwRuntimeError('Library name mismatch: ' + name)
     }
     return value;
   }
   dart.import = import_;
+
+  function initializeLibraryStub(name) {
+    // Create the library object if necessary.
+    if (!dart.global[name]) {
+      dart.global[name] = {};
+    }
+    return dart.global[name];
+  }
   
-  function lazyImport(value) {
-    return defineLibrary(value, {});
+  function lazyImport(name) {
+    return initializeLibraryStub(name);
   }
   dart.lazyImport = lazyImport;
 
-  function defineLibrary(value, defaultValue) {
-    return value ? value : defaultValue;
+  function defineLibrary(name, defaultValue) {
+    if (loadedLibraries[name]) {
+      throwRuntimeError('Library is already defined: ' + name);
+    }
+    var value;
+    if (defaultValue) {
+      var oldValue = dart.global[name];
+      if (oldValue && oldValue != defaultValue) {
+        throwRuntimeError('Library ' + name + ' cannot be redefined to ' + defaultValue);

[Jennifer Messerly, 2015/06/05 16:22:27]

long line.
also could use interpolation:

`Library ${name} cannot be ...`

[vsm, 2015/06/05 17:01:04]

Done.

+      }
+      dart.global[name] = value = defaultValue;
+    } else {
+      value = initializeLibraryStub(name);
+    }
+    loadedLibraries[name] = value;
+    return value;
   }
   dart.defineLibrary = defineLibrary;