[Console] Following link to large file from Console doesn't react for a while

[digitarald]

STR:

• Fresh Nightly profile
• Open https://discourse.mozilla.org/t/things-i-miss-about-firebug/17233
• Open Console
• Click the file for the Ember tooling notice
• Keep clicking

AR:

• Nothing happens for me, for about 10sec, then Debugger opens with the file (not correct line)

ER:

• Open Debugger and show the file with the right line

[digitarald]

Same on Github, takes 3sec to click:

[juliandescottes]

For the record, the workaround I used on #4705 also makes the performance of this scenario much better.

[jasonLaster]

I just looked into this and the slow down comes from our current strategy of blocking opening the debugger on fetching all of the sources.

• We fetch all the sources because the debugger can open after the page is open
• We block because when a user clicks a link in the console, we check to see if the debugger has the source before deciding to show the source in view-source or the debugger.

We can speed up the debugger opening by not blocking:

diff --git a/src/client/firefox.js b/src/client/firefox.js
index 0715faf..fb0a6d1 100644
--- a/src/client/firefox.js
+++ b/src/client/firefox.js
@@ -45,9 +45,9 @@ export async function onConnect(connection: any, actions: Object): Object {
   // the debugger (if it's paused already, or if loading the page from
   // bfcache) so explicity fire `newSource` events for all returned
   // sources.
-  const sources = await clientCommands.fetchSources();
+  clientCommands.fetchSources().then(sources => actions.newSources(sources));
+
   await actions.connect(tabTarget.url);
-  await actions.newSources(sources);

   // If the threadClient is already paused, make sure to show a
   // paused state.

navigating to viewSource

We can check the source map url service to see if the source has been seen before opening the debugger

Note

One thing to watch out for if we stop blocking the debugger opening is that we scroll when the source loads.

[jasonLaster]

Here is a sketch of what the changes could look like in the panel:

diff --git a/devtools/client/framework/source-map-url-service.js b/devtools/client/framework/source-map-url-service.js
index fe4ff87..f2940f7 100644
--- a/devtools/client/framework/source-map-url-service.js
+++ b/devtools/client/framework/source-map-url-service.js
@@ -347,4 +347,6 @@ SourceMapURLService.prototype._onPrefChanged = function () {
   }
 };
 
+SourceMapURLService.prototype.hasSource = // YAY
+ 
 exports.SourceMapURLService = SourceMapURLService;
diff --git a/devtools/client/shared/view-source.js b/devtools/client/shared/view-source.js
index 94a6dff..3ec74b6 100644
--- a/devtools/client/shared/view-source.js
+++ b/devtools/client/shared/view-source.js
@@ -59,8 +59,7 @@ exports.viewSourceInDebugger = Task.async(function* (toolbox, sourceURL, sourceL
 
   // New debugger frontend
   if (Services.prefs.getBoolPref("devtools.debugger.new-debugger-frontend")) {
-    const source = dbg.getSource(sourceURL);
-    if (source) {
+    if (toolbox.sourceMapService.hasSource(sourceURL)) {
       yield toolbox.selectTool("jsdebugger");
       dbg.selectSource(sourceURL, sourceLine);
return true;

[codehag]

p1 of this fix: https://reviewboard.mozilla.org/r/222292/

[digitarald]

Works snappy for me now.