The Sage Trac Server

Sometimes you will only want to work on local changes to Sage, for your own private needs. However, typically it is beneficial to share code and ideas with others; the manner in which the Sage project does this (as well as fixing bugs and upgrading components) is in a very collaborative and public setting on the Sage Trac server (the Sage bug and enhancement tracker).

The purpose of the Sage trac server is to

  1. Provide a place for discussion on issues and store a permanent record.

  2. Provide a repository of source code and all proposed changes.

  3. Link these two together.

There is also a wiki for more general organizational web pages, like Sage development workshops.

Thus if you find a bug in Sage, if you have new code to submit, want to review new code already written but not yet included in Sage, or if you have corrections for the documentation, you should post on the trac server. Items on the server are called tickets, and anyone may search or browse the tickets. For a list of recent changes, just visit the Sage trac timeline.

Obtaining an Account

New: Previously, it was necessary to manually request a Trac account in order to post anything to Sage’s Trac. Now, if you have a GitHub account, you may log in using it to create and comment on tickets, and edit wiki pages on Sage’s Trac.

A manual account request is currently only necessary if you prefer not to use GitHub or if you want to log into the old Sage Wiki. This may change as well in the future.

To obtain a non-GitHub account, send an email to containing:

  • your full name,

  • preferred username,

  • contact email,

  • and reason for needing a trac account

Your trac account also grants you access to the sage wiki. Make sure you understand the review process, and the procedures for opening and closing tickets before making changes. The remainder of this chapter contains various guidelines on using the trac server.

Trac authentication through SSH

There are two avenues to prove to the trac server that you are who you claim to be. First, to change the ticket web pages you need to log in to trac using a username/password. Second, there is public key cryptography used by git when copying new source files to the repository. This section will show you how to set up both.

Generating and Uploading your SSH Keys

The git installation on the development server uses SSH keys to decide if and where you are allowed to upload code. No SSH key is required to report a bug or comment on a ticket, but as soon as you want to contribute code yourself you need to provide trac with the public half of your own personal key. Details are described in the following two sections.

Generating your SSH Keys

If you don’t have a private key yet, you can create it with the ssh-keygen tool:

[[email protected] ~]$ ssh-keygen
Generating public/private rsa key pair.
Enter file in which to save the key (/home/user/.ssh/id_rsa):
Enter passphrase (empty for no passphrase):
Enter same passphrase again:
Your identification has been saved in /home/user/.ssh/id_rsa.
Your public key has been saved in /home/user/.ssh/
The key fingerprint is:
ce:32:b3:de:38:56:80:c9:11:f0:b3:88:f2:1c:89:0a [email protected]
The key's randomart image is:
+--[ RSA 2048]----+
|  ....           |
|   ..            |
|   .o+           |
| o o+o.          |
|E + .  .S        |
|+o .   o.        |
|. o   +.o        |
|      oB         |
|     o+..        |

This will generate a new random private RSA key in the .ssh folder in your home directory. By default, they are


Your private key. Keep safe. Never hand it out to anybody.


The corresponding public key. This and only this file can be safely disclosed to third parties.

The ssh-keygen tool will let you generate a key with a different file name, or protect it with a passphrase. Depending on how much you trust your own computer or system administrator, you can leave the passphrase empty to be able to login without any human intervention.

If you have accounts on multiple computers you can use the SSH keys to log in. Just copy the public key file (ending in .pub) to ~/.ssh/authorized_keys on the remote computer and make sure that the file is only read/writeable by yourself. Voila, the next time you ssh into that machine you don’t have to provide your password.

Linking your Public Key to your Trac Account

The Sage trac server needs to know one of your public keys. You can upload it in the preferences, that is

  1. Go to

  2. Log in with your trac username/password

  3. Click on “Preferences”

  4. Go to the “SSH Keys” tab

  5. Paste the content of your public key file (e.g. ~/.ssh/

  6. Click on “Save changes”

Note that this does not allow you to ssh into any account on trac, it is only used to authenticate you to the gitolite installation on trac. You can test that you are being authenticated correctly by issuing some basic gitolite commands, for example:

[[email protected] ~]$ ssh [email protected] info
hello user, this is [email protected] running gitolite3 (unknown) on git

 R W      sage
[[email protected] ~]$ ssh [email protected] help
hello user, this is gitolite3 (unknown) on git

list of remote commands available:


Reporting Bugs

If you think you have found a bug in Sage, here is the procedure:

  • Search through our Google groups for postings related to your possible bug (it may have been fixed/reported already):

    Similarly, you can search The Sage Trac Server to see if anyone else has opened a ticket about your bug.

  • If you do not find anything, and you are not sure that you have found a bug, ask about it on sage-devel. A bug report should contain:

    • An explicit and reproducible example illustrating your bug (and/or the steps required to reproduce the buggy behavior).

    • The version of Sage you run, as well as the version of the optional packages that may be involved in the bug.

    • Describe your operating system as accurately as you can and your architecture (32-bit, 64-bit, …).

  • You might be asked to open a new ticket. In this case, follow the Guidelines for Opening Tickets.

Thank you in advance for reporting bugs to improve Sage in the future!

Guidelines for Opening Tickets

In addition to bug reports (see Reporting Bugs), you should also open a ticket if you have some new code that makes Sage a better tool. If you have a feature request, start a discussion on sage-devel first, and then if there seems to be general agreement that you have a good idea, open a ticket describing the idea.

  • Do you already have a trac account? If not, click here.

Before opening a new ticket, consider the following points:

  • Make sure that nobody else has opened a ticket about the same or closely related issue.

  • It is much better to open several specific tickets than one that is very broad. Indeed, a single ticket which deals with lots of different issues can be quite problematic, and should be avoided.

  • Be precise: If foo does not work on OS X but is fine on Linux, mention that in the title. Use the keyword option so that searches will pick up the issue.

  • The problem described in the ticket must be solvable. For example, it would be silly to open a ticket whose purpose was “Make Sage the best mathematical software in the world”. There is no metric to measure this properly and it is highly subjective.

  • For bug reports: the ticket’s description should contain the information described at Reporting Bugs.

  • If appropriate, provide URLs to background information or sage-devel conversation relevant to the problem you are reporting.

When creating the ticket, you may find useful to read The Ticket Fields.

Unless you know what you are doing, leave the milestone field to its default value.

The Ticket Fields

When you open a new ticket or change an existing ticket, you will find a variety of fields that can be changed. Here is a comprehensive overview (for the ‘status’ field, see The status of a ticket):

  • Reported by: The trac account name of whoever created the ticket. Cannot be changed.

  • Owned by: Trac account name of owner, by default the person in charge of the Component (see below). Generally not used in the Sage trac.

  • Type: One of enhancement (e.g. a new feature), defect (e.g. a bug fix), or task (rarely used).

  • Priority: The priority of the ticket. Keep in mind that the “blocker” label should be used very sparingly.

  • Milestone: Milestones are usually goals to be met while working toward a release. In Sage’s trac, we use milestones instead of releases. Each ticket must have a milestone assigned. If you are unsure, assign it to the current milestone.

  • Component: A list of components of Sage, pick one that most closely matches the ticket.

  • Keywords: List of keywords. Fill in any keywords that you think will make your ticket easier to find. Tickets that have been worked on at Sage days NN (some number) ofter have sdNN as keyword.

  • Cc: List of trac user names to Cc (send emails for changes on the ticket). Note that users that enter a comment are automatically substcribed to email updates and don’t need to be listed under Cc.

  • Merged in: The Sage release where the ticket was merged in. Only changed by the release manager.

  • Authors: Real name of the ticket author(s).

  • Reviewers: Real name of the ticket reviewer(s).

  • Report Upstream: If the ticket is a bug in an upstream component of Sage, this field is used to summarize the communication with the upstream developers.

  • Work issues: Issues that need to be resolved before the ticket can leave the “needs work” status.

  • Branch: The Git branch containing the ticket’s code (see Branching Out). It is displayed in green color, unless there is a conflict between the branch and the latest beta release (red color). In this case, the branch should be merged or rebased.

  • Dependencies: Does the ticket depend on another ticket? Sometimes, a ticket requires that another ticket be applied first. If this is the case, put the dependencies as a comma-separated list (#1234, #5678) into the “Dependencies:” field.

  • Stopgaps: See Stopgaps.

The status of a ticket

The status of a ticket appears right next to its number, at the top-left corner of its page. It indicates who has to work on it.

  • new – the ticket has only been created (or the author forgot to change the status to something else).

    If you want to work on it yourself it is better to leave a comment to say so. It could avoid having two persons doing the same job.

  • needs_review – the code is ready to be peer-reviewed. If the code is not yours, then you can review it. See The reviewer’s check list.

  • needs_work – something needs to be changed in the code. The reason should appear in the comments.

  • needs_info – somebody has to answer a question before anything else can happen. It should be clear from the comments.

  • positive_review – the ticket has been reviewed, and the release manager will close it.

The status of a ticket can be changed using a form at the bottom of the ticket’s page. Leave a comment explaining your reasons whenever you change it.


When Sage returns wrong results, two tickets should be opened:

  • A main ticket with all available details.

  • A “stopgap” ticket (e.g. trac ticket #12699)

This second ticket does not fix the problem but adds a warning that will be printed whenever anyone uses the relevant code. This, until the problem is finally fixed.

To produce the warning message, use code like the following:

from sage.misc.stopgap import stopgap
stopgap("This code contains bugs and may be mathematically unreliable.",

Replace TICKET_NUM by the ticket number for the main ticket. On the main trac ticket, enter the ticket number for the stopgap ticket in the “Stopgaps” field (see The Ticket Fields). Stopgap tickets should be marked as blockers.


If mathematically valid code causes Sage to raise an error or crash, for example, there is no need for a stopgap. Rather, stopgaps are to warn users that they may be using buggy code; if Sage crashes, this is not an issue.

Working on Tickets

If you manage to fix a bug or enhance Sage you are our hero. See Sage Development Process for making changes to the Sage source code, uploading them to the Sage trac server, and finally putting your new branch on the trac ticket. The following are some other relevant issues:

  • The Patch buildbot will automatically test your ticket. See the patchbot wiki for more information about its features and limitations. Make sure that you look at the log, especially if the patch buildbot did not give you the green blob.

  • Every bug fixed should result in a doctest.

  • This is not an issue with defects, but there are many enhancements possible for Sage and too few developers to implement all the good ideas. The trac server is useful for keeping ideas in a central place because in the Google groups they tend to get lost once they drop off the first page.

  • If you are a developer, be nice and try to solve a stale/old ticket every once in a while.

  • Some people regularly do triage. In this context, this means that we look at new bugs and classify them according to our perceived priority. It is very likely that different people will see priorities of bugs very differently from us, so please let us know if you see a problem with specific tickets.

Reviewing and closing Tickets

Tickets can be closed when they have positive review or for other reasons. To learn how to review, please see The reviewer’s check list.

Only the Sage release manager will close tickets. Most likely, this is not you nor will your trac account have the necessary permissions. If you feel strongly that a ticket should be closed or deleted, then change the status of the ticket to needs review and change the milestone to sage-duplicate/invalid/wontfix. You should also comment on the ticket, explaining why it should be closed. If another developer agrees, he sets the ticket to positive review.

A related issue is re-opening tickets. You should refrain from re-opening a ticket that is already closed. Instead, open a new ticket and provide a link in the description to the old ticket.

Reasons to Invalidate Tickets

One Issue Per Ticket: A ticket must cover only one issue and should not be a laundry list of unrelated issues. If a ticket covers more than one issue, we cannot close it and while some of the patches have been applied to a given release, the ticket would remain in limbo.

No Patch Bombs: Code that goes into Sage is peer-reviewed. If you show up with an 80,000 lines of code bundle that completely rips out a subsystem and replaces it with something else, you can imagine that the review process will be a little tedious. These huge patch bombs are problematic for several reasons and we prefer small, gradual changes that are easy to review and apply. This is not always possible (e.g. coercion rewrite), but it is still highly recommended that you avoid this style of development unless there is no way around it.

Sage Specific: Sage’s philosophy is that we ship everything (or close to it) in one source tarball to make debugging possible. You can imagine the combinatorial explosion we would have to deal with if you replaced only ten components of Sage with external packages. Once you start replacing some of the more essential components of Sage that are commonly packaged (e.g. Pari, GAP, lisp, gmp), it is no longer a problem that belongs in our tracker. If your distribution’s Pari package is buggy for example, file a bug report with them. We are usually willing and able to solve the problem, but there are no guarantees that we will help you out. Looking at the open number of tickets that are Sage specific, you hopefully will understand why.

No Support Discussions: The trac installation is not meant to be a system to track down problems when using Sage. Tickets should be clearly a bug and not “I tried to do X and I couldn’t get it to work. How do I do this?” That is usually not a bug in Sage and it is likely that sage-support can answer that question for you. If it turns out that you did hit a bug, somebody will open a concise and to-the-point ticket.

Solution Must Be Achievable: Tickets must be achievable. Many times, tickets that fall into this category usually ran afoul to some of the other rules listed above. An example would be to “Make Sage the best CAS in the world”. There is no metric to measure this properly and it is highly subjective.