See errors in buffers¶
When a syntax check in the current buffer has finished Flycheck reports the results of the check in the current buffer in two ways:
- Highlight errors, warnings, etc. directly in the buffer according to
- Indicate errors, warnings, etc. in the fringe according to
Additionally Flycheck indicates its current state and the number of errors and warnings in the mode line.
The following screenshot illustrates how this looks like in the default Emacs color theme. It shows an info, a warning and an error annotation, from top to bottom. Please also note the fringe indicators on the left side and the emphasized mode line indicator in the bottom right corner:
The colours of fringe icons and the whole appearance of the error highlights depend on the active color theme. Although red, orange and green or blue seem to be somewhat standard colours for Flycheck’s annotations across many popular themes, please take a closer look at your color theme if you’re in doubt about the meaning of a Flycheck highlight.
All errors that syntax checkers report have a level which tells you the severity of the error. Flycheck has three built-in levels:
- Severe errors like syntax or type errors.
- Potential but not fatal mistakes which you should likely fix nonetheless.
- Purely informational messages which inform about notable things in the current buffer, or provide additional help to fix errors or warnings.
Each error level has a distinct highlighting and colour which helps you to identify the severity of each error right in the buffer.
Flycheck highlights errors directly in the buffer according to
flycheck-highlighting-mode. By default these highlights consist of a coloured
wave underline which spans the whole symbol at the error location as in the
screenshot above but the highlights are entirely customisable. You can change
the extents of highlighting or disable it completely with
flycheck-highlighting-mode, or customise Flycheck’s faces to change the style
of the underline or use different colours.
How Flycheck highlights errors and warnings in the buffer:
- Do not highlight anything at all.
- Highlight the whole line and discard any information about the column.
- Highlight the column of the error if any, otherwise like
- Highlight the entire symbol around the error column if any, otherwise like
columns. This is this default.
- Highlight the entire expression around the error column if any, otherwise
In some major modes
sexpsis very slow, because discovering expression boundaries efficiently is hard.
python-modeis known to suffer from this issue.
Be careful when enabling this mode.
The highlights use the following faces depending on the error level:
In GUI frames Flycheck also adds indicators to the fringe—the left or right border of an Emacs window that is—to help you identify erroneous lines quickly. These indicators consist of a rightward-pointing double arrow shape coloured in the colour of the corresponding error level.
Flycheck extensions can define custom error levels with different fringe indicators. Furthermore some Emacs distributions like Spacemacs redefine Flycheck’s error levels to use different indicators. If you’re using such a distribution please take a look at its documentation if you’re unsure about the appearance of Flycheck’s indicators.
Note that we discourage you from changing the shape of Flycheck’s fringe indicators.
You can customise the location of these indicators (left or right fringe) with
flycheck-indication-mode which also lets you turn off these indicators
How Flycheck indicates errors and warnings in the buffer fringes:
- Use the left or right fringe respectively.
- Do not indicate errors and warnings in the fringe.
The following faces control the colours of the fringe indicators. However they
do not let you change the shape of the indicators—to achieve this you’d have to
redefine the error levels with
Like all minor modes Flycheck also has a mode line indicator. You can see it in the bottom right corner of the above screenshot. By default the indicator shows Flycheck’s current state via one of the following texts:
||Flycheck is checking the buffer currently.|
||There are no errors or warnings in the current buffer.|
||There are three errors and five warnings in the current buffer.|
||Flycheck did not find a syntax checker for the current buffer.
Take a look at the list of supported languages and type
||The last syntax check failed. Inspect the
||The last syntax check had a dubious result. The definition of a
syntax checker may have a bug. Inspect the
You can entirely customise the mode line indicator with
A “mode line construct” for Flycheck’s mode line indicator.
To avoid flooding a buffers with excessive highlighting, cluttering the
appearance and slowing down Emacs, Flycheck takes precautions against syntax
checkers that report a large number of errors exceeding
The maximum number of errors a syntax checker is allowed to report.
If a syntax checker reports more errors the error information is discarded. To not run into the same issue again on the next syntax check the syntax checker is automatically added to
flycheck-disabled-checkersin this case to disable it for the next syntax check.
You can explicitly remove all highlighting and indication and all error information from a buffer:
C-c ! C¶
Clear all reported errors, all highlighting and all indication icons from the current buffer.