Features and usage

There are two main features:

  • detection of old annotations (FIXME, TODO, etc.);
  • detection of forgotten FUTURE tags.

Detection of old annotations

Rationale and principles

Developers use annotations to indicate that some code is deficient: FIXME, TODO, OPTIMIZE, HACK, BUG, etc. Semantics vary, but the overall meaning is the same: the annotated code should be changed, some day. Sometimes very soon, sometimes hypothetically.

Time passes and these annotations tend to be forgotten or ignored.

check-fixmes warns about annotations that it considers too old. It is then the developer’s choice to act: remove the annotation (because we decided it is not worth to fix, or because it is not relevant anymore), change the code, or postpone the annotation.

The only way to postpone an annotation is to commit a change on its line. To simplify that, a good habit is to indicate today’s date beside the annotation. The date can then be quickly updated without changing the rest of the line (nor its length) when we decide to postpone. Example:

FIXME (2020-01-04): I am getting heartburn. Tony, do something terrible.

Note that this date is not taken in account by check-fixmes to calculate the age of the annotation. We found that it was not useful and possibly error-prone. Instead, the date of the last commit is used.

Usage and possible customization

$ check-fixmes --help
usage: check-fixmes [-h] [--conf CONF] [--max-age MAX_AGE] [--no-color] [--xunit-file XUNIT_FILE] [path]

Check your code for unattended annotations

positional arguments:
  path                  Git-managed path where search should happen. Defaults to the working directory.

optional arguments:
  -h, --help            show this help message and exit
  --conf CONF           Path of the configuration file. Defaults to pyproject.toml if it exists.
  --max-age MAX_AGE     Maximum age in days allowed for an annotation, errors otherwise. Defaults to 180.
  --no-color            Do not colorize errors. Defaults to colorizing errors in red.
  --xunit-file XUNIT_FILE
                        Path of the xUnit report file to write. Defaults to no xUnit output.

The age of the annotation is calculated from the time of the last commit that touched the line the annotation appears on.

The author of each annotation is reported, again by looking at the last commit that touched the line. You may also assign someone else by formatting your annotation like this:

FIXME (jsmith): It is up to John to do something here.

As suggested above, you can indicate a date to more easily postpone the FIXME. The default format looks like this:

FIXME (jsmith, 2020-04-01): It is up to John to do something here.

You can mark a line as not to be reported with the string no-check-fixmes. This is useful if you are using a word that would be an annotation, but not in this context. For example, in a CSS file:

div {
  background: url('img/todo.png'); /* no-check-fixmes */

If you need to ignore whole files, see the whitelist option.

Possible customizations:

See the Configuration section below for full details.

Detection of orphan FUTURE tags

Rationale and principles

Developers sometimes plan a broad modification that will span multiple files. Instead of littering FIXME annotations everywhere, they can set a single FIXME annotation and a FUTURE-xxx tag on the same line. Then, wherever we need to make a modification, we only mention this FUTURE-xxx tag without any FIXME. If we have to “postpone” a FIXME, there is only line to touch.


# in
#     FIXME (jsmith, FUTURE-SWITCH-TO-V2): remove this field when we switch to v2
# in
#     FUTURE-SWITCH-TO-V2: deprecate usage when we switch to v2

If we ever remove the FIXME but keep the FUTURE-SWITCH-TO-V2 tag in, it is a mistake and check-fixmes warns us.

Usage and possible customization

check-fixmes looks for tags that start with FUTURE- (e.g. FUTURE-SWITCH-TO-V2) to make sure that at least one of them appears on the same line as an annotation. If not, it is considered an orphan tag and is reported as an error.

As for annotations, you can ignore a line by using no-check-fixmes, and ignore whole files with the whitelist option. You can configure how tags are detected with the future_tag_regex option.

See the Configuration section below for full details.


check-fixmes takes its configuration from a TOML file. By default and if present, pyproject.toml is read (as a courtesy for Python projects, even though check-fixmes is language-agnostic). A limited list of options can be overridden via command line arguments (that you can list with check-fixmes --help). Such overrides take precedence over the values defined in the configuration files (or the default values if omitted).

The TOML configuration file should have a [tool.check-fixmes] section, like this:

path = "src"
max-age = 30

For an example configuration file, see the configuration file of the check-oldies project itself.

Here is the list of all options that can be configured via the TOML configuration file:

Input options

path (overridable via the command line)

The path of the directory in which check-fixmes looks for annotations (recursively). It must be a Git checkout repository.

Type: string.
Default: "." (current working directory).
Example: path = "src".


If the no-check-fixmes pragma is not appropriate, you may whitelist whole files by providing a list of glob patterns.

Type: list.
Default: [] (no whitelist).
Example: whitelist = ["docs/*"].

Output options


By default, errors (old annotations and orphan FUTURE tags) appear in red. Set this option to false if you want to use the default foreground color.

Type: boolean.
Default: true.
Example: colorize-errors = false.

xunit-file (overridable via the command line)

The path to the xUnit report file to generate. check-fixmes gracefully creates parent directories of the file if they do not exist.

Type: string (a path).
Default: none (no xUnit file is generated).
Example: xunit-file = "reports/xunit.xml".

Detection options


The list of annotations to look for. Note that check-fixmes is case insensitive: by default, both “todo”, “TODO”, “fixme” and “FIXME” will be reported.

Type: list.
Default: ["fixme", "todo"] (case insensitive).
Example: annotations = ["todo", "optimize", "fixme", "hack"].


The regular expression (using Python syntax) to use to extract the assignee in an annotation. Requirements:

  • it should contain the string {annotation_regex}. check-fixmes will replace it by the proper regex that match all annotations;
  • it must have a group named assignee.
Type: string (a Python regular expression).
Default: "(?:{annotation_regex})\s*\((?P<assignee>\w+)" (matches FIXME (jsmith)).
Example: assignee-regex = "(?:{annotation_regex})\s*- (?P<assignee>\w+)" (matches FIXME - jsmith).


The extended regular expression to use to detect FUTURE tags.

Type: string (an extended regular expression).
Default: "FUTURE-[-[:alnum:]\._]+?".
Example: future-tag-regex = "HEREAFTER-[-[:alnum:]\._]+?".


The list of annotations which will not trigger orphan FUTURE tags checks. Note that check-fixmes is case insensitive: by default, both “wontfix”, “WONTFIX” will be ignored.

Type: list.
Default: ["wontfix", "xxx"] (case insensitive).
Example: ignored_annotations = ["wontfix", "nofix"].

max-age (overridable via the command line)

The age (in days) above which an annotation is considered old.

Type: integer.
Default: 180.
Example: max-age = 30.