File.realPath().

Not tested yet, because we can't create symlinks from Wren and I don't
want to check symlinks into the repo, but it seems to do the right
thing.

doc/site/modules/io/file.markdown

@@ -51,6 +51,15 @@ No encoding or decoding is done. If the file is UTF-8, then the resulting
 string will be a UTF-8 string. Otherwise, it will be a string of bytes in
 whatever encoding the file uses.
 
+### File.**realPath**(path)
+
+Resolves `path`, traversing symlinks and removining any unneeded `./` and `../`
+components. Returns the canonical absolute path to the file.
+
+    :::wren
+    var path = "/some/./symlink/a/../b/file.txt"
+    System.print(File.realPath(path)) //> /real/path/a/file.txt
+
 ### File.**size**(path)
 
 Returns the size in bytes of the contents of the file at `path`.

src/cli/modules.c

@@ -17,6 +17,7 @@ extern void fileSizePath(WrenVM* vm);
 extern void fileClose(WrenVM* vm);
 extern void fileDescriptor(WrenVM* vm);
 extern void fileReadBytes(WrenVM* vm);
+extern void fileRealPath(WrenVM* vm);
 extern void fileSize(WrenVM* vm);
 extern void fileStat(WrenVM* vm);
 extern void fileWriteBytes(WrenVM* vm);
@@ -115,6 +116,7 @@ static ModuleRegistry modules[] =
       FINALIZER(fileFinalize)
       STATIC_METHOD("delete_(_,_)", fileDelete)
       STATIC_METHOD("open_(_,_,_)", fileOpen)
+      STATIC_METHOD("realPath_(_,_)", fileRealPath)
       STATIC_METHOD("sizePath_(_,_)", fileSizePath)
       METHOD("close_(_)", fileClose)
       METHOD("descriptor", fileDescriptor)

src/module/io.c

@@ -302,6 +302,23 @@ void fileReadBytes(WrenVM* vm)
              fileReadBytesCallback);
 }
 
+static void realPathCallback(uv_fs_t* request)
+{
+  if (handleRequestError(request)) return;
+  
+  wrenEnsureSlots(getVM(), 3);
+  wrenSetSlotString(getVM(), 2, (char*)request->ptr);
+  schedulerResume(freeRequest(request), true);
+  schedulerFinishResume();
+}
+
+void fileRealPath(WrenVM* vm)
+{
+  const char* path = wrenGetSlotString(vm, 1);
+  uv_fs_t* request = createRequest(wrenGetSlotValue(vm, 2));
+  uv_fs_realpath(getLoop(), request, path, realPathCallback);
+}
+
 // Called by libuv when the stat call completes.
 static void statCallback(uv_fs_t* request)
 {

src/module/io.wren

@@ -91,6 +91,14 @@ foreign class File {
     return File.open(path) {|file| file.readBytes(file.size) }
   }
 
+  // TODO: This works for directories too, so putting it on File is kind of
+  // lame. Consider reorganizing these classes some.
+  static realPath(path) {
+    ensurePath_(path)
+    realPath_(path, Fiber.current)
+    return Scheduler.runNextScheduled_()
+  }
+
   static size(path) {
     ensurePath_(path)
     sizePath_(path, Fiber.current)
@@ -158,6 +166,7 @@ foreign class File {
 
   foreign static delete_(path, fiber)
   foreign static open_(path, flags, fiber)
+  foreign static realPath_(path, fiber)
   foreign static sizePath_(path, fiber)
 
   foreign close_(fiber)

src/module/io.wren.inc

@@ -93,6 +93,14 @@ static const char* ioModuleSource =
 "    return File.open(path) {|file| file.readBytes(file.size) }\n"
 "  }\n"
 "\n"
+"  // TODO: This works for directories too, so putting it on File is kind of\n"
+"  // lame. Consider reorganizing these classes some.\n"
+"  static realPath(path) {\n"
+"    ensurePath_(path)\n"
+"    realPath_(path, Fiber.current)\n"
+"    return Scheduler.runNextScheduled_()\n"
+"  }\n"
+"\n"
 "  static size(path) {\n"
 "    ensurePath_(path)\n"
 "    sizePath_(path, Fiber.current)\n"
@@ -160,6 +168,7 @@ static const char* ioModuleSource =
 "\n"
 "  foreign static delete_(path, fiber)\n"
 "  foreign static open_(path, flags, fiber)\n"
+"  foreign static realPath_(path, fiber)\n"
 "  foreign static sizePath_(path, fiber)\n"
 "\n"
 "  foreign close_(fiber)\n"

test/io/file/real_path_nonexistent.wren

@@ -0,0 +1,3 @@
+import "io" for File
+
+File.realPath("nonexistent") // expect runtime error: no such file or directory

test/io/file/real_path_wrong_arg_type.wren

@@ -0,0 +1,6 @@
+import "io" for File
+
+File.realPath(123) // expect runtime error: Path must be a string.
+
+// TODO: Write success case tests too when we have an API to create symlinks
+// from Wren.