Support completion when cursor inside an argument (#4023)

* Support completion when cursor inside an argument

Bash supports completion even when cursor is in an argument, this is very useful for some fixup after the initial completion.
Let add this feature as well.

Signed-off-by: Tw <wei.tan@intel.com>

* Add test for when cursor inside an argument

To support test this case, let's also take the position into account.

Signed-off-by: Tw <wei.tan@intel.com>

crates/nu-completion/src/engine.rs

@@ -238,11 +238,19 @@ pub fn completion_location(line: &str, block: &Block, pos: usize) -> Vec<Complet
                                 }
                             }
 
-                            output.push(loc.clone());
+                            output.push({
+                                let mut partial_loc = loc.clone();
+                                partial_loc.span = Span::new(loc.span.start(), pos);
+                                partial_loc
+                            });
                             output
                         }
                     }
-                    _ => vec![loc.clone()],
+                    _ => vec![{
+                        let mut partial_loc = loc.clone();
+                        partial_loc.span = Span::new(loc.span.start(), pos);
+                        partial_loc
+                    }],
                 };
             } else if pos < loc.span.start() {
                 break;
@@ -339,7 +347,7 @@ mod tests {
             line: &str,
             scope: &dyn ParserScope,
             pos: usize,
-        ) -> Vec<LocationType> {
+        ) -> Vec<CompletionLocation> {
             let (tokens, _) = lex(line, 0, nu_parser::NewlineMode::Normal);
             let (lite_block, _) = parse_block(tokens);
 
@@ -348,9 +356,6 @@ mod tests {
             scope.exit_scope();
 
             super::completion_location(line, &block, pos)
-                .into_iter()
-                .map(|v| v.item)
-                .collect()
         }
 
         #[test]
@@ -362,7 +367,7 @@ mod tests {
 
             assert_eq!(
                 completion_location(line, &registry, 10),
-                vec![LocationType::Command],
+                vec![LocationType::Command.spanned(Span::new(9, 10)),],
             );
         }
 
@@ -373,7 +378,7 @@ mod tests {
 
             assert_eq!(
                 completion_location(line, &registry, 10),
-                vec![LocationType::Command],
+                vec![LocationType::Command.spanned(Span::new(9, 10)),],
             );
         }
 
@@ -384,7 +389,7 @@ mod tests {
 
             assert_eq!(
                 completion_location(line, &registry, 4),
-                vec![LocationType::Command],
+                vec![LocationType::Command.spanned(Span::new(0, 4)),],
             );
         }
 
@@ -395,7 +400,7 @@ mod tests {
 
             assert_eq!(
                 completion_location(line, &registry, 13),
-                vec![LocationType::Variable],
+                vec![LocationType::Variable.spanned(Span::new(5, 13)),],
             );
         }
 
@@ -410,7 +415,7 @@ mod tests {
 
             assert_eq!(
                 completion_location(line, &registry, 7),
-                vec![LocationType::Flag("du".to_string())],
+                vec![LocationType::Flag("du".to_string()).spanned(Span::new(3, 7)),],
             );
         }
 
@@ -421,7 +426,7 @@ mod tests {
 
             assert_eq!(
                 completion_location(line, &registry, 8),
-                vec![LocationType::Command],
+                vec![LocationType::Command.spanned(Span::new(6, 8)),],
             );
         }
 
@@ -433,8 +438,8 @@ mod tests {
             assert_eq!(
                 completion_location(line, &registry, 3),
                 vec![
-                    LocationType::Command,
+                    LocationType::Command.spanned(Span::new(0, 3)),
-                    LocationType::Argument(Some("cd".to_string()), None)
+                    LocationType::Argument(Some("cd".to_string()), None).spanned(Span::new(3, 3)),
                 ],
             );
         }
@@ -451,8 +456,8 @@ mod tests {
             assert_eq!(
                 completion_location(line, &registry, 3),
                 vec![
-                    LocationType::Argument(Some("du".to_string()), None),
+                    LocationType::Argument(Some("du".to_string()), None).spanned(Span::new(3, 4)),
-                    LocationType::Flag("du".to_string()),
+                    LocationType::Flag("du".to_string()).spanned(Span::new(3, 4)),
                 ],
             );
         }
@@ -467,8 +472,24 @@ mod tests {
             assert_eq!(
                 completion_location(line, &registry, 6),
                 vec![
-                    LocationType::Command,
+                    LocationType::Command.spanned(Span::new(0, 6)),
-                    LocationType::Argument(Some("echo".to_string()), None)
+                    LocationType::Argument(Some("echo".to_string()), None).spanned(Span::new(5, 6)),
+                ],
+            );
+        }
+
+        #[test]
+        fn completes_argument_when_cursor_inside_argument() {
+            let registry: VecRegistry =
+                vec![Signature::build("echo").rest("rest", SyntaxShape::Any, "the values to echo")]
+                    .into();
+            let line = "echo 123";
+
+            assert_eq!(
+                completion_location(line, &registry, 6),
+                vec![
+                    LocationType::Command.spanned(Span::new(0, 6)),
+                    LocationType::Argument(Some("echo".to_string()), None).spanned(Span::new(5, 6)),
                 ],
             );
         }