Bisecting a Regression

The minimum requirements are Git and Node.js.

Clone PDF.js

• Open the Git command line.
• Change to a directory where you want to place PDF.js.
• Run git clone git://github.com/mozilla/pdf.js.git.

Start PDF.js

Using Node.js

• Run cd pdf.js.
• Run npx gulp server.
• Open a browser and visit http://localhost:8080/web/viewer.html.

Using another server

• Open a browser and go to http://<yourserver>/pdf.js/web/viewer.html.

Verify the regression

Download the bad PDF and open it with the above viewer (using, for example, the "Open File" button in the toolbar) and verify that rendering the PDF is broken.

Start the bisection process

Mark the current version as bad using git bisect start and git bisect bad.

Find the bad commit ID

Using the commit/version of PDF.js installed in Firefox

• Open resource://pdf.js/build/pdf.js.
• Find the commit in the line with PDFJS.build =.
• Find the version in the line with PDFJS.version =.

Using a Bugzilla patch

A Bugzilla patch contains the commit information near browser/extensions/pdfjs/content/build/pdf.js, e.g., see https://bug871530.bugzilla.mozilla.org/attachment.cgi?id=750657 (was added3d (good), will be 869b878 (bad)).

Using DXR

If you know it was good in the Beta branch, get the bad commit ID from DXR. Find the line with PDFJS.build = and copy the value in the single quotes, for example 4e83123. You can find PDF.js on DXR at https://dxr.mozilla.org/mozilla-beta/source/browser/extensions/pdfjs/content/build/pdf.js.

Verify the working version

• Run git checkout <commit ID that you found above>.
• Do a full refresh (CTRL + Shift + R) Firefox and verify that rendering of the PDF is no longer broken.
• Mark it as good with git bisect good.

Continue bisecting

• Do a full refresh (CTRL + Shift + R) of the viewer in Firefox.
• If the current version works, mark it using git bisect good.
• If the current version does not work, mark it using git bisect bad.
• Repeat the steps above until it converges to a single commit.