use sys.displayhook when running interactively, rather than printing directly

Author: timfel

graalpython/com.oracle.graal.python.shell/src/com/oracle/graal/python/shell/GraalPythonMain.java

@@ -608,7 +608,11 @@ public int readEvalPrint(Context context, ConsoleHandler consoleHandler) {
                     while (true) { // processing subsequent lines while input is incomplete
                         lastStatus = 0;
                         try {
-                            context.eval(Source.newBuilder(getLanguageId(), sb.toString(), "<stdin>").interactive(true).buildLiteral());
+                            Value result = context.eval(Source.newBuilder(getLanguageId(), sb.toString(), "<stdin>").interactive(true).buildLiteral());
+                            Value displayhook = sys.getMember("displayhook");
+                            if (displayhook != null && displayhook.canExecute()) {
+                                displayhook.execute(result);
+                            }
                         } catch (PolyglotException e) {
                             if (continuePrompt == null) {
                                 continuePrompt = doEcho ? sys.getMember("ps2").asString() : null;

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/PythonLanguage.java

@@ -343,7 +343,13 @@ public static PythonCore getCore() {
 
     @Override
     protected boolean isVisible(PythonContext context, Object value) {
-        return value != PNone.NONE && value != PNone.NO_VALUE;
+        if (PythonOptions.getOption(context, PythonOptions.TerminalIsInteractive)) {
+            // if we run through our own launcher, the sys.__displayhook__ would provide the
+            // printing
+            return false;
+        } else {
+            return value != PNone.NONE && value != PNone.NO_VALUE;
+        }
     }
 
     @Override

graalpython/lib-graalpython/sys.py

@@ -204,3 +204,27 @@ def breakpointhook(*args, **kws):
 @__builtin__
 def getrecursionlimit():
     return 1000
+
+
+@__builtin__
+def displayhook(value):
+    if value is None:
+        return
+    builtins = modules['builtins']
+    # Set '_' to None to avoid recursion
+    builtins._ = None
+    text = repr(value)
+    try:
+        stdout.write(text)
+    except UnicodeEncodeError:
+        bytes = text.encode(stdout.encoding, 'backslashreplace')
+        if hasattr(stdout, 'buffer'):
+            stdout.buffer.write(bytes)
+        else:
+            text = bytes.decode(stdout.encoding, 'strict')
+            stdout.write(text)
+    stdout.write("\n")
+    builtins._ = value
+
+
+__displayhook__ = displayhook