[gjs: 4/5] debugger: Refactor throw and return commands

[Cosimo Cecchi <cosimoc src gnome org>]

commit 7c8ae6392f766ab56ed0ca1955c94efd9a2bcf29
Author: Philip Chimento <philip chimento gmail com>
Date:   Sun Jul 22 23:20:15 2018 -0400

    debugger: Refactor throw and return commands
    
    They are very similar, so they can share almost all of their code. At the
    same time, use early returns in the refactored function to avoid some
    nesting.

 modules/_bootstrap/debugger.js | 69 ++++++++++++++++--------------------------
 1 file changed, 26 insertions(+), 43 deletions(-)
---
diff --git a/modules/_bootstrap/debugger.js b/modules/_bootstrap/debugger.js
index 357cb126..8c75bb6a 100644
--- a/modules/_bootstrap/debugger.js
+++ b/modules/_bootstrap/debugger.js
@@ -266,31 +266,39 @@ function continueCommand() {
     return [undefined];
 }
 
-function throwCommand(rest) {
+function throwOrReturn(rest, action, defaultCompletion) {
     if (focusedFrame !== topFrame) {
         print("To throw, you must select the newest frame (use 'frame 0').");
         return;
-    } else if (focusedFrame === null) {
+    }
+    if (focusedFrame === null) {
         print('No stack.');
         return;
-    } else if (rest === '') {
-        return [{throw: lastExc}];
-    } else {
-        var cv = saveExcursion(() => focusedFrame.eval(rest));
-        if (cv === null) {
-            if (!dbg.enabled)
-                return [cv];
-            print('Debuggee died while determining what to throw. Stopped.');
-        } else if ('return' in cv) {
-            return [{throw: cv['return']}];
-        } else {
-            if (!dbg.enabled)
-                return [cv];
-            print('Exception determining what to throw. Stopped.');
-            showDebuggeeValue(cv.throw);
-        }
+    }
+    if (rest === '')
+        return [defaultCompletion];
+
+    const cv = saveExcursion(() => focusedFrame.eval(rest));
+    if (cv === null) {
+        if (!dbg.enabled)
+            return [cv];
+        print(`Debuggee died while determining what to ${action}. Stopped.`);
         return;
     }
+    if ('return' in cv)
+        return [{[action]: cv['return']}];
+    if (!dbg.enabled)
+        return [cv];
+    print(`Exception determining what to ${action}. Stopped.`);
+    showDebuggeeValue(cv.throw);
+}
+
+function throwCommand(rest) {
+    return throwOrReturn(rest, 'throw', {throw: lastExc});
+}
+
+function returnCommand(rest) {
+    return throwOrReturn(rest, 'return', {return: undefined});
 }
 
 function frameCommand(rest) {
@@ -346,31 +354,6 @@ function downCommand() {
     }
 }
 
-function returnCommand(rest) {
-    const f = focusedFrame;
-    if (f !== topFrame) {
-        print("To return, you must select the newest frame (use 'frame 0').");
-    } else if (f === null) {
-        print('Nothing on the stack.');
-    } else if (rest === '') {
-        return [{return: undefined}];
-    } else {
-        const cv = saveExcursion(() => f.eval(rest));
-        if (cv === null) {
-            if (!dbg.enabled)
-                return [cv];
-            print('Debuggee died while determining what to return. Stopped.');
-        } else if ('return' in cv) {
-            return [{return: cv['return']}];
-        } else {
-            if (!dbg.enabled)
-                return [cv];
-            print('Error determining what to return. Stopped.');
-            showDebuggeeValue(cv.throw);
-        }
-    }
-}
-
 function printPop(c) {
     if (c['return']) {
         print('Value returned is:');