From 6c08b04b31382ba11fac3c5f0a76ff07c814d7bc Mon Sep 17 00:00:00 2001
From: "Alexis (Poliorcetics) Bourget" <ab_jujutsu@poliorcetiq.eu>
Date: Mon, 1 Apr 2024 18:54:45 +0200
Subject: [PATCH] feat: add autocompletion for diff-source command

---
 helix-term/src/commands/typed.rs |  2 +-
 helix-term/src/ui/mod.rs         | 10 ++++++++++
 helix-vcs/src/lib.rs             | 29 ++++++++++++++++++++++++++++-
 3 files changed, 39 insertions(+), 2 deletions(-)

diff --git a/helix-term/src/commands/typed.rs b/helix-term/src/commands/typed.rs
index 98856680eb3de..523c483d78e86 100644
--- a/helix-term/src/commands/typed.rs
+++ b/helix-term/src/commands/typed.rs
@@ -3076,7 +3076,7 @@ pub const TYPABLE_COMMAND_LIST: &[TypableCommand] = &[
         aliases: &[],
         doc: "Set the diff source for the file. If no argument is provided, show the current source.",
         fun: diff_source,
-        signature: CommandSignature::none(),
+        signature: CommandSignature::all(completers::diff_source),
     },
     TypableCommand {
         name: "clear-register",
diff --git a/helix-term/src/ui/mod.rs b/helix-term/src/ui/mod.rs
index b5969818cf563..6e351c8fd67c1 100644
--- a/helix-term/src/ui/mod.rs
+++ b/helix-term/src/ui/mod.rs
@@ -259,6 +259,7 @@ pub mod completers {
     use crate::ui::prompt::Completion;
     use helix_core::fuzzy::fuzzy_match;
     use helix_core::syntax::LanguageServerFeature;
+    use helix_vcs::DiffSource;
     use helix_view::document::SCRATCH_BUFFER_NAME;
     use helix_view::theme;
     use helix_view::{editor::Config, Editor};
@@ -399,6 +400,15 @@ pub mod completers {
         })
     }
 
+    pub fn diff_source(_editor: &Editor, input: &str) -> Vec<Completion> {
+        let iter = DiffSource::all_values();
+
+        fuzzy_match(input, iter, false)
+            .into_iter()
+            .map(|(&name, _)| ((0..), name.into()))
+            .collect()
+    }
+
     #[derive(Copy, Clone, PartialEq, Eq)]
     enum FileMatch {
         /// Entry should be ignored
diff --git a/helix-vcs/src/lib.rs b/helix-vcs/src/lib.rs
index 50cb787b17f4b..29a0d0335306f 100644
--- a/helix-vcs/src/lib.rs
+++ b/helix-vcs/src/lib.rs
@@ -125,6 +125,25 @@ impl DiffSource {
             }
         });
     }
+
+    /// Used to offer completion options for the `diff-source` command
+    pub fn all_values() -> &'static [&'static str] {
+        // To force a miscompilation and remember to add the value to the list
+        match Self::None {
+            Self::None => (),
+            #[cfg(feature = "git")]
+            Self::File => (),
+            Self::Git => (),
+        }
+
+        // Keep it sorted alphabetically
+        &[
+            "file",
+            #[cfg(feature = "git")]
+            "git",
+            "none",
+        ]
+    }
 }
 
 impl FromStr for DiffSource {
@@ -136,7 +155,7 @@ impl FromStr for DiffSource {
             "file" => Ok(Self::File),
             #[cfg(feature = "git")]
             "git" => Ok(Self::Git),
-            s => bail!("invalid diff source '{s}', pick one of 'none', 'file' or 'git'"),
+            s => bail!("invalid diff source '{s}'"),
         }
     }
 }
@@ -175,4 +194,12 @@ mod tests {
         #[cfg(feature = "git")]
         assert_eq!(DiffSource::Git.to_string(), "git");
     }
+
+    #[test]
+    fn test_diff_source_all_values() {
+        let all = DiffSource::all_values();
+        let mut all_sorted = all.to_vec();
+        all_sorted.sort_unstable();
+        assert_eq!(all, all_sorted);
+    }
 }