Bug 1572280 Part 3 - Reparse sources with GC'ed scripts to get all breakpoint positions, r=loganfsmyth.

Depends on D41127

Differential Revision: https://phabricator.services.mozilla.com/D41128

--HG--
extra : moz-landing-system : lando

devtools/client/debugger/test/mochitest/browser.ini

@@ -164,3 +164,4 @@ skip-if = (os == 'linux' && debug) || (os == 'linux' && asan) || ccov  #Bug 1456
 [browser_dbg-message-run-to-completion.js]
 [browser_dbg-remember-expanded-scopes.js]
 [browser_dbg-bfcache.js]
+[browser_dbg-gc-breakpoint-positions.js]

devtools/client/debugger/test/mochitest/browser_dbg-gc-breakpoint-positions.js

@@ -0,0 +1,15 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at <http://mozilla.org/MPL/2.0/>. */
+
+"use strict";
+
+// Test that we can set breakpoints in scripts that have been GCed.
+
+add_task(async function() {
+  const dbg = await initDebugger("doc-gc-breakpoint-positions.html",
+                                 "doc-gc-breakpoint-positions.html");
+  await selectSource(dbg, "doc-gc-breakpoint-positions.html");
+  await addBreakpoint(dbg, "doc-gc-breakpoint-positions.html", 21);
+  ok(true, "Added breakpoint at GC'ed script location");
+});

devtools/client/debugger/test/mochitest/examples/doc-gc-breakpoint-positions.html

@@ -0,0 +1,23 @@
+<div>
+  Here
+  is
+  some
+  stuff
+  so
+  that
+  the
+  source's
+  start
+  line
+  is
+  not
+  one
+</div>
+<script>
+// Make sure the source stays alive.
+function foo() {
+}
+// After the outer script has been GC'ed, breakpoints can't be set here.
+var x = null;
+setTimeout(() => SpecialPowers.gc(), 0);
+</script>

devtools/server/actors/source.js

@@ -384,6 +384,29 @@ const SourceActor = ActorClassWithSpec(sourceSpec, {
 
     const scripts = this._findDebuggeeScripts();
 
+    // We need to find all breakpoint positions, even if scripts associated with
+    // this source have been GC'ed. We detect this by looking for a script which
+    // does not have a function: a source will typically have a top level
+    // non-function script. If this top level script still exists, then it keeps
+    // all its child scripts alive and we will find all breakpoint positions by
+    // scanning the existing scripts. If the top level script has been GC'ed
+    // then we won't find its breakpoint positions, and inner functions may have
+    // been GC'ed as well. In this case we reparse the source and generate a new
+    // and complete set of scripts to look for the breakpoint positions.
+    // Note that in some cases like "new Function(stuff)" there might not be a
+    // top level non-function script, but if there is a non-function script then
+    // it must be at the top level and will keep all other scripts in the source
+    // alive.
+    const isWasm = this._source.introductionType === "wasm";
+    if (!isWasm && !scripts.some(script => !script.isFunction)) {
+      scripts.length = 0;
+      function addScripts(script) {
+        scripts.push(script);
+        script.getChildScripts().forEach(addScripts);
+      }
+      addScripts(this._source.reparse());
+    }
+
     const positions = [];
     for (const script of scripts) {
       // This purely a performance boost to avoid needing to build an array