Add Stdin.isTerminal.

doc/site/modules/io/stdin.markdown

@@ -16,6 +16,12 @@ Defaults to `false`.
 
 Sets raw mode on or off.
 
+### **isTerminal**
+
+Returns `true` if Stdin is connected to a "TTY". This is true when the user is
+running Wren in an interactive terminal, and false if it its input is coming
+from a pipe.
+
 ### **readByte**()
 
 Reads one byte of input from stdin. Blocks the current fiber until a byte has

src/cli/modules.c

@@ -39,6 +39,7 @@ extern void statIsDirectory(WrenVM* vm);
 extern void statIsFile(WrenVM* vm);
 extern void stdinIsRaw(WrenVM* vm);
 extern void stdinIsRawSet(WrenVM* vm);
+extern void stdinIsTerminal(WrenVM* vm);
 extern void stdinReadStart(WrenVM* vm);
 extern void stdinReadStop(WrenVM* vm);
 extern void schedulerCaptureMethods(WrenVM* vm);
@@ -147,6 +148,7 @@ static ModuleRegistry modules[] =
     CLASS(Stdin)
       STATIC_METHOD("isRaw", stdinIsRaw)
       STATIC_METHOD("isRaw=(_)", stdinIsRawSet)
+      STATIC_METHOD("isTerminal", stdinIsTerminal)
       STATIC_METHOD("readStart_()", stdinReadStart)
       STATIC_METHOD("readStop_()", stdinReadStop)
     END_CLASS

src/module/io.c

@@ -539,6 +539,12 @@ void stdinIsRawSet(WrenVM* vm)
   }
 }
 
+void stdinIsTerminal(WrenVM* vm)
+{
+  initStdin();
+  wrenSetSlotBool(vm, 0, uv_guess_handle(stdinDescriptor) == UV_TTY);
+}
+
 static void allocCallback(uv_handle_t* handle, size_t suggestedSize,
                           uv_buf_t* buf)
 {

src/module/io.wren

@@ -217,6 +217,7 @@ foreign class Stat {
 class Stdin {
   foreign static isRaw
   foreign static isRaw=(value)
+  foreign static isTerminal
 
   static readByte() {
     return read_ {

src/module/io.wren.inc

@@ -219,6 +219,7 @@ static const char* ioModuleSource =
 "class Stdin {\n"
 "  foreign static isRaw\n"
 "  foreign static isRaw=(value)\n"
+"  foreign static isTerminal\n"
 "\n"
 "  static readByte() {\n"
 "    return read_ {\n"

test/io/stdin/is_terminal.wren

@@ -0,0 +1,4 @@
+import "io" for Stdin
+
+// The tests aren't run in a terminal.
+System.print(Stdin.isTerminal) // expect: false