Implement repr() for file objects

src/runtime/builtin_modules/builtins.cpp

@@ -213,7 +213,7 @@ Box* open(Box* arg1, Box* arg2) {
     if (!f)
         raiseExcHelper(IOError, "%s: '%s' '%s'", strerror(errno), fn.c_str());
 
-    return new BoxedFile(f);
+    return new BoxedFile(f, fn, mode);
 }
 
 extern "C" Box* chr(Box* arg) {

src/runtime/builtin_modules/sys.cpp

@@ -112,9 +112,9 @@ void setupSys() {
 
     sys_module->giveAttr("argv", new BoxedList());
 
-    sys_module->giveAttr("stdout", new BoxedFile(stdout));
-    sys_module->giveAttr("stdin", new BoxedFile(stdin));
-    sys_module->giveAttr("stderr", new BoxedFile(stderr));
+    sys_module->giveAttr("stdout", new BoxedFile(stdout, "<stdout>", "w"));
+    sys_module->giveAttr("stdin", new BoxedFile(stdin, "<stdin>", "r"));
+    sys_module->giveAttr("stderr", new BoxedFile(stderr, "<stderr>", "w"));
 
     sys_module->giveAttr("warnoptions", new BoxedList());
     sys_module->giveAttr("py3kwarning", False);

src/runtime/file.cpp

@@ -26,7 +26,14 @@ namespace pyston {
 
 Box* fileRepr(BoxedFile* self) {
     assert(self->cls == file_cls);
-    RELEASE_ASSERT(0, "");
+
+    void* addr = static_cast<void*>(self->f);
+    std::ostringstream repr;
+
+    repr << "<" << (self->closed ? "closed" : "open") << " file '" << self->fname << "', ";
+    repr << "mode '" << self->fmode << "' at " << addr << ">";
+
+    return boxString(repr.str());
 }
 
 Box* fileRead(BoxedFile* self, Box* _size) {

src/runtime/types.h

@@ -290,9 +290,12 @@ extern "C" BoxedTuple* EmptyTuple;
 class BoxedFile : public Box {
 public:
     FILE* f;
+    std::string fname;
+    std::string fmode;
     bool closed;
     bool softspace;
-    BoxedFile(FILE* f) __attribute__((visibility("default"))) : Box(file_cls), f(f), closed(false), softspace(false) {}
+    BoxedFile(FILE* f, std::string fname, std::string fmode) __attribute__((visibility("default")))
+    : Box(file_cls), f(f), fname(fname), fmode(fmode), closed(false), softspace(false) {}
 };
 
 struct PyHasher {

test/tests/file.py

+import sys
+
 f = open("/dev/null")
 print repr(f.read())
 
@@ -6,3 +8,23 @@ print repr(f2.read())
 
 with open("/dev/null") as f3:
     print repr(f3.read())
+
+# String representation of file objects.
+def chop(s):
+    """Chop off the last bit of a file object repr, which is the address
+    of the raw file pointer.
+    """
+    return ' '.join(s.split()[:-1])
+
+for desc in [sys.stderr, sys.stdout, sys.stdin]:
+    print chop(str(desc))
+
+f = open("/dev/null", 'w')
+print chop(str(f))
+f.close()
+print chop(str(f))
+
+f = open("/dev/null", 'r')
+print chop(str(f))
+f.close()
+print chop(str(f))