4.3.2 Suffix Specifications ¶

A transient’s suffix and infix commands are bound when the transient prefix command is defined using transient-define-prefix, see Defining Transients. The commands are organized into groups, see Group Specifications. Here we describe the form used to bind an individual suffix command.

The same form is also used when later binding additional commands using functions such as transient-insert-suffix, see Modifying Existing Transients.

Note that an infix is a special kind of suffix. Depending on context “suffixes” means “suffixes (including infixes)” or “non-infix suffixes”. Here it means the former.

Suffix specifications have this form:

([LEVEL] [KEY [DESCRIPTION]] COMMAND|ARGUMENT [KEYWORD VALUE]...)

LEVEL, KEY and DESCRIPTION can also be specified using the KEYWORDs :level, :key and :description. If the object that is associated with COMMAND sets these properties, then they do not have to be specified here. You can however specify them here anyway, possibly overriding the object’s values just for the binding inside this transient.

• LEVEL is the suffix level, an integer between 1 and 7. See Enabling and Disabling Suffixes.
• KEY is the key binding, a string in the format returned by describe-key and understood by kbd.

  That format is more permissive than the one accepted by key-valid-p. Being more permissive makes it possible, for example, to write the key binding, which toggles the -a command line argument, as "-a", instead of having to write "- a". Likewise additional spaces can be added, which is not removed when displaying the binding in the menu, which is useful for alignment purposes.

• DESCRIPTION is the description, either a string or a function that takes zero or one arguments (the suffix object) and returns a string. The function should be a lambda expression to avoid ambiguity. In some cases a symbol that is bound as a function would also work but to be safe you should use :description in that case.

The next element is either a command or an argument. This is the only argument that is mandatory in all cases.

• COMMAND should be a symbol that is bound as a function, which has to be defined or at least autoloaded as a command by the time the containing prefix command is invoked.

  Any command will do; it does not need to have an object associated with it (as would be the case if transient-define-suffix or transient-define-infix were used to define it).

  COMMAND can also be a lambda expression.

  As mentioned above, the object that is associated with a command can be used to set the default for certain values that otherwise have to be set in the suffix specification. Therefore if there is no object, then you have to make sure to specify the KEY and the DESCRIPTION.

  As a special case, if you want to add a command that might be neither defined nor autoloaded, you can use a workaround like:

  (transient-insert-suffix 'some-prefix "k"
    '("!" "Ceci n'est pas une commande" no-command
      :if (lambda () (featurep 'no-library))))
  

  Instead of featurep you could also use require with a non-nil value for NOERROR.

• The mandatory argument can also be a command-line argument, a string. In that case an anonymous command is defined and bound.

  Instead of a string, this can also be a list of two strings, in which case the first string is used as the short argument (which can also be specified using :shortarg) and the second as the long argument (which can also be specified using :argument).

  Only the long argument is displayed in the menu buffer. See transient-detect-key-conflicts for how the short argument may be used.

  Unless the class is specified explicitly, the appropriate class is guessed based on the long argument. If the argument ends with ‘=’ (e.g., ‘--format=’) then transient-option is used, otherwise transient-switch.

Finally, details can be specified using optional KEYWORD-VALUE pairs. Each keyword has to be a keyword symbol, either :class or a keyword argument supported by the constructor of that class. See Suffix Slots.

If a keyword argument accepts a function as value, you an use a lambda expression. As a special case, the ## macro (which returns a lambda expression and is implemented in the llama package) is also supported. Inside suffix bindings, the use of ## is not supported anywhere but directly following a keyword symbol.