[wasm] Add inspector test for stepping

test/inspector/debugger/wasm-stepping.js

Index: test/inspector/debugger/wasm-stepping.js
diff --git a/test/inspector/debugger/wasm-stepping.js b/test/inspector/debugger/wasm-stepping.js
new file mode 100644
index 0000000000000000000000000000000000000000..944e1c6031d5832be7bc1931b092851048c18d8f
--- /dev/null
+++ b/test/inspector/debugger/wasm-stepping.js
@@ -0,0 +1,179 @@
+// Copyright 2017 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+load('test/mjsunit/wasm/wasm-constants.js');
+load('test/mjsunit/wasm/wasm-module-builder.js');
+
+var builder = new WasmModuleBuilder();
+
+var func_a_idx =
+    builder.addFunction('wasm_A', kSig_v_v).addBody([kExprNop, kExprNop]).index;
+
+// wasm_B calls wasm_A <param0> times.
+builder.addFunction('wasm_B', kSig_v_i)
+    .addBody([
+      // clang-format off
+      kExprLoop, kWasmStmt,               // while
+        kExprGetLocal, 0,                 // -
+        kExprIf, kWasmStmt,               // if <param0> != 0
+          kExprGetLocal, 0,               // -
+          kExprI32Const, 1,               // -
+          kExprI32Sub,                    // -
+          kExprSetLocal, 0,               // decrease <param0>
+          kExprCallFunction, func_a_idx,  // -
+          kExprBr, 1,                     // continue
+          kExprEnd,                       // -
+        kExprEnd,                         // break
+      // clang-format on
+    ])
+    .exportAs('main');
+
+var module_bytes = builder.toArray();
+
+function instantiate(bytes) {
+  var buffer = new ArrayBuffer(bytes.length);
+  var view = new Uint8Array(buffer);
+  for (var i = 0; i < bytes.length; ++i) {
+    view[i] = bytes[i] | 0;
+  }
+
+  var module = new WebAssembly.Module(buffer);
+  // Set global variable.
+  instance = new WebAssembly.Instance(module);
+}
+
+var addSourceUrl = (code, url) => '//# sourceURL=' + url + '\n' + code;

[kozy, 2017/01/25 18:04:59]

Usually sourceURL comment is last line of source.

[Clemens Hammacher, 2017/01/25 21:06:11]

Done.

+
+function evalThen(expr, url, next) {
+  var promise = Protocol.Runtime.evaluate(
+      {'expression': addSourceUrl(expr, 'v8://test/' + url)});
+  if (next) promise = promise.then(next);
+  return promise;
+}
+
+Protocol.Debugger.onScriptParsed(handleScriptParsed);
+Protocol.Debugger.onPaused(handlePaused);
+var wasm_B_scriptId;
+var step_actions = [
+  'stepInto',  // == stepOver, to call instruction
+  'stepInto',  // into call to wasm_A
+  'stepOver',  // over first nop
+  'stepOut',   // out of wasm_A
+  'stepOut',   // out of wasm_B, stop on breakpoint again
+  'stepOver',  // to call
+  'stepOver',  // over call
+  'resume',    // to next breakpoint (third iteration)
+  'stepInto',  // to call
+  'stepInto',  // into wasm_A
+  'stepOut',   // out to wasm_B
+  // now step 9 times, until we are in wasm_A again.
+  'stepInto', 'stepInto', 'stepInto', 'stepInto', 'stepInto', 'stepInto',
+  'stepInto', 'stepInto', 'stepInto',
+  // 3 more times, back to wasm_B.
+  'stepInto', 'stepInto', 'stepInto',
+  // then just resume.
+  'resume'
+];
+var sources = {};
+var urls = {};
+var afterTwoSourcesCallback;
+
+InspectorTest.runTestSuite([

[kozy, 2017/01/25 18:04:59]

We usually use it when test contains set of small tests, this usage is probably
fine, but you definitely could rewrite this test using promises and avoid some
introduced helper functions.

[Clemens Hammacher, 2017/01/25 21:06:11]

Changed it.

+  function enableDebugger(next) {
+    Protocol.Debugger.enable().then(next);
+  },
+
+  function defineInstance(next) {
+    evalThen('var instance;', 'defineInstance', next);
+  },
+
+  function defineInstantiateFunction(next) {
+    evalThen(instantiate.toString(), 'defineInstantiateFunction', next);
+  },
+
+  function callInstantiate(next) {
+    afterTwoSourcesCallback = next;
+    evalThen(
+        'instantiate(' + JSON.stringify(module_bytes) + ')', 'callInstantiate');
+  },
+
+  function setBreakpoint(next) {
+    if (!wasm_B_scriptId) {
+      InspectorTest.log('Missing wasm_B script id');
+    }
+    InspectorTest.log(
+        'Setting breakpoint on line 7 (on the setlocal before the call)');
+    Protocol.Debugger
+        .setBreakpoint(
+            {'location': {'scriptId': wasm_B_scriptId, 'lineNumber': 7}})
+        .then(msg => InspectorTest.logMessage(msg))

[kozy, 2017/01/25 18:04:59]

.then(InspectorTest.logMessage)

[Clemens Hammacher, 2017/01/25 21:06:11]

Done.

+        .then(next);
+  },
+
+  function runTestFunction(next) {
+    evalThen('instance.exports.main(4)', 'runWasm')
+        .then(() => InspectorTest.log('exports.main returned!'))
+        .then(next);
+  },
+
+  function finished(next) {
+    InspectorTest.log('Finished!');
+    next();
+  }
+]);
+
+function getSourceFromMessage(message) {
+  if (!message.result || !message.result.scriptSource) {
+    InspectorTest.logMessage(message);
+    return '';
+  }
+  return message.result.scriptSource;
+}
+
+function handleScriptParsed(msg) {
+  var url = msg.params.url;
+  if (!url.startsWith('wasm://')) {
+    InspectorTest.log('Ignoring script with url ' + url);
+    return;
+  }
+  var scriptId = msg.params.scriptId;
+  urls[scriptId] = url;
+  InspectorTest.log('Got wasm script: ' + url);
+  if (url.substr(-2) == '-1') wasm_B_scriptId = scriptId;
+  InspectorTest.log('Requesting source...');
+  function printAndStoreSource(src) {
+    InspectorTest.log(src);
+    sources[scriptId] = src;
+    if (Object.keys(sources).length == 2) afterTwoSourcesCallback();

[kozy, 2017/01/25 18:04:59]

You could right this logic in following way:
Protocol.Debugger.onceScriptParsed().then(scriptParsed).then(next);

function scriptParsed(message) {
// process script
if (enoughtScripts) return;
else return Protocol.Debugger.onceScriptParsed().then(scriptParsed);
}

I just prefer to see tests where I can just read from the top to bottom to
understand what actually happening without jumping from top to bottom and back.

And mixing callbacks and promises look not good.

[Clemens Hammacher, 2017/01/25 21:06:11]

Done.
I hope I will get better in writing these tests one day ;)

+  }
+
+  Protocol.Debugger.getScriptSource({scriptId: scriptId})
+      .then(msg => printAndStoreSource(getSourceFromMessage(msg)));
+}
+
+function printPauseLocation(scriptId, lineNr, columnNr) {
+  var lines = sources[scriptId].split('\n');
+  var line = '<illegal line number>';
+  if (lineNr < lines.length) {
+    line = lines[lineNr];
+    if (columnNr < line.length) {
+      line = line.substr(0, columnNr) + '>' + line.substr(columnNr);
+    }
+  }
+  InspectorTest.log(
+      'Paused at ' + urls[scriptId] + ':' + lineNr + ':' + columnNr + ': ' +
+      line);
+}
+
+function handlePaused(msg) {
+  var loc = msg.params.callFrames[0].location;
+  printPauseLocation(loc.scriptId, loc.lineNumber, loc.columnNumber);
+  var action = step_actions.shift();
+  InspectorTest.log('Step action: ' + action);

[kozy, 2017/01/25 18:04:59]

move this line to else block of following if, otherwise you'll 'Step action:
undefined'

[Clemens Hammacher, 2017/01/25 21:06:11]

As this is not supposed to happen, I just removed the check for undefined.

+  if (!action) {
+    InspectorTest.log('Undefined step action! Assuming resume.');
+    action = 'resume';
+  }
+  Protocol.Debugger[action]();
+}