Package yacspin
provides yet another CLi spinner for Go, taking inspiration
(and some utility code) from the github.com/briandowns/spinner
project. Specifically yacspin
borrows the default character sets and color name mappings to
github.com/fatih/color colors.
Because this package adopts the spinner character sets from github.com/briandowns/spinner, this package is released under the Apache 2.0 License. The full content of the Apache 2.0 license is available in the included LICENSE file in the root of this repository.
This project was created after it was realized that the most popular spinner library for Go had some limitations, that couldn't be fixed without a massive overhaul of the API.
The other spinners tie the ability to show updated messages to the spinner's animation, meaning you can't always show all the information you want to the end user without changing the animation speed. This results in having to trade off animation aesthetics to show "realtime" information. It was a goal to avoid this problem and instead render the animation independently from the contents being updated. An example of this is shown below.
In addition, there were also some API design choices that have made
github.com/briandowns/spinner
unsafe for concurrent use,
which presents challenges when trying to update the text in the spinner while
it's animating. This could result in undefined behavior due to data races.
There were also some variable-width spinners in that project that did not render
correctly. Because the width of the spinner animation would change, so would the
position of the message on the screen. yacspin
uses a dynamic width when
animating, so your message should appear static relative to the animating
spinner. There is also an example of this feature blow.
Finally, there was an interest in the spinner being able to represent a task, and to indicate whether it failed or was successful. This would have further compounded the API changes needed above to support in an intuitive way.
This project is inspired by github.com/briandowns/spinner, and takes a new approach to address some of the challenges and limitations it has.
There are over 90 spinners available in the CharSets
package variable. They
were borrowed from github.com/briandowns/spinner.
There is a table with most of the spinners at the bottom of this README.
Because of how some spinners are animated, they may have different widths at
different frames in the animation. yacspin
calculates the maximum width of the
animation, and then adds padding to ensure the text's position on the screen
doesn't change. This results in a smoother looking animation:
The spinner has both Stop()
and StopFail()
methods, which allow the
spinner to result in a success message or a failure message. The messages,
colors, and even the character used to denote success or failure are
customizable in either the initial config or via the spinner's methods.
By doing this you can use a single yacspin
spinner to display the status of a
list of tasks being executed serially:
The SpinnerAtEnd
field of the Config
struct allows you to specify whether
the spinner is rendered at the end of the line instead of the beginning. The
default value (false
) results in the spinner being rendered at the beginning
of the line.
The spinner is safe for concurrent use, so you can update any of its settings via methods whether the spinner is stopped or is currently animating.
Many spinners tie the ability to show new messages to the animation of the spinner itself. So if the spinner animates every 200ms, you can only show updated information every 200ms. If you wanted more frequent updates, you'd need to tradeoff the asthetics of the animation to display more data.
yacspin
updates the printed information of the spinner immediately on
change, without the animation updating. This allows you to use an animation
speed that looks astheticaly pleasing, while also knowing the data presented to
the user will be updated live.
You can see this in action in the following gif, where the filenames being uploaded are rendered independent of the spinner being animated:
Sometimes you want to change a few settings, and don't want the yacspin
spinner to render your partially applied configuration. If your spinner is
running, and you want to change a few configuration items via method calls, you
can Pause()
the spinner first. After making the changes you can call
Unpause()
, and it will continue rendering like normal with the newly applied
configuration. yacspin
will then continue rendering the animation, while
triggering the next animation to happen as close as possible to the next
Frequency period if it hasn't already passed.
yacspin
also has native support for non-interactive (TTY) output targets. By
default this is detected in the constructor, or can be overriden via the
TerminalMode
Config
struct field. When detecting the application is not
running withn a TTY session, the behavior of the spinner is different.
Specifically, when this is automatically detected the spinner no longer uses colors, disables the automatic spinner animation, and instead only animates the spinner when updating the message. In addition, each animation is rendered on a new line instead of overwriting the current line.
This should result in human-readable output without any changes needed by consumers, even when the system is writing to a non-TTY destination.
If you'd like to manually animate the spinner, you can do so by setting the
TerminalMode
to ForceNoTTYMode | ForceSmartTerminalMode
. In this mode the
spinner will still use colors and other text stylings, but the animation only
happens when data is updated and on individual lines. You can accomplish this by
calling the Message()
method with the same used previously.
go get github.com/theckman/yacspin
Within the yacspin
package there are some default spinners stored in the
yacspin.CharSets
variable, and you can also provide your own. There is also a
list of known colors in the yacspin.ValidColors
variable.
There are runnable examples in the examples/ directory, with one simple example and one more advanced one. Here is a quick snippet showing usage from a very high level, with error handling omitted:
cfg := yacspin.Config{
Frequency: 100 * time.Millisecond,
CharSet: yacspin.CharSets[59],
Suffix: " backing up database to S3",
SuffixAutoColon: true,
Message: "exporting data",
StopCharacter: "✓",
StopColors: []string{"fgGreen"},
}
spinner, err := yacspin.New(cfg)
// handle the error
err = spinner.Start()
// doing some work
time.Sleep(2 * time.Second)
spinner.Message("uploading data")
// upload...
time.Sleep(2 * time.Second)
err = spinner.Stop()
The spinner animations below are recorded at a refresh frequency of 200ms. Some animations may look better at a different speed, so play around with the frequency until you find a value you find aesthetically pleasing.