[[completion]]
= Completion

ifndef::snippets[:snippets: ../../test/java/org/springframework/shell/docs]

Spring Shell can provide completion proposals for both interactive shell
and a command-line. There are differences however as when shell is in
interactive mode we have an active instance of a shell meaning it's
easier to provide more programmatic ways to provide completion hints.
When shell is purely run as a command-line tool a completion can only
be accomplished with integration into OS level shell's like _bash_.

[[interactive]]
== Interactive

Hints for completions are calculated with _function_ or _interface_ style
methods which takes `CompletionContext` and returns a list of
`CompletionProposal` instances. `CompletionContext` gives you various
information about a current context like command registration and option.

NOTE: Generic resolvers can be registered as a beans if those are useful
for all commands and scenarious. For example existing completion
implementation `RegistrationOptionsCompletionResolver` handles completions
for a option names.

[source, java, indent=0]
----
include::{snippets}/CompletionSnippets.java[tag=resolver-1]
----

Option values with builder based command registration can be
defined per option.

[source, java, indent=0]
----
include::{snippets}/CompletionSnippets.java[tag=builder-1]
----

Option values with annotation based command registration are handled
via `ValueProvider` interface which can be defined with `@ShellOption`
annotation.

[source, java, indent=0]
----
include::{snippets}/CompletionSnippets.java[tag=provider-1]
----

Actual `ValueProvider` with annotation based command needs to be
registered as a _Bean_.

[source, java, indent=0]
----
include::{snippets}/CompletionSnippets.java[tag=anno-method]
----

[[command-line]]
== Command-Line

Command-line completion currently only support _bash_ and is documented
in a built-in `completion` command xref:using-shell-commands-builtin-completion.adoc[Completion].