1 files changed, 94 insertions, 0 deletions

diff --git a/crates/completion/src/render/builder_ext.rs b/crates/completion/src/render/builder_ext.rs
new file mode 100644
index 000000000..37b0d0459
--- /dev/null
+++ b/crates/completion/src/render/builder_ext.rs
@@ -0,0 +1,94 @@
+//! Extensions for `Builder` structure required for item rendering.
+
+use itertools::Itertools;
+use test_utils::mark;
+
+use crate::{item::Builder, CompletionContext};
+
+pub(super) enum Params {
+    Named(Vec<String>),
+    Anonymous(usize),
+}
+
+impl Params {
+    pub(super) fn len(&self) -> usize {
+        match self {
+            Params::Named(xs) => xs.len(),
+            Params::Anonymous(len) => *len,
+        }
+    }
+
+    pub(super) fn is_empty(&self) -> bool {
+        self.len() == 0
+    }
+}
+
+impl Builder {
+    pub(super) fn should_add_parems(&self, ctx: &CompletionContext) -> bool {
+        if !ctx.config.add_call_parenthesis {
+            return false;
+        }
+        if ctx.use_item_syntax.is_some() {
+            mark::hit!(no_parens_in_use_item);
+            return false;
+        }
+        if ctx.is_pattern_call {
+            mark::hit!(dont_duplicate_pattern_parens);
+            return false;
+        }
+        if ctx.is_call {
+            return false;
+        }
+
+        // Don't add parentheses if the expected type is some function reference.
+        if let Some(ty) = &ctx.expected_type {
+            if ty.is_fn() {
+                mark::hit!(no_call_parens_if_fn_ptr_needed);
+                return false;
+            }
+        }
+
+        // Nothing prevents us from adding parentheses
+        true
+    }
+
+    pub(super) fn add_call_parens(
+        mut self,
+        ctx: &CompletionContext,
+        name: String,
+        params: Params,
+    ) -> Builder {
+        if !self.should_add_parems(ctx) {
+            return self;
+        }
+
+        let cap = match ctx.config.snippet_cap {
+            Some(it) => it,
+            None => return self,
+        };
+        // If not an import, add parenthesis automatically.
+        mark::hit!(inserts_parens_for_function_calls);
+
+        let (snippet, label) = if params.is_empty() {
+            (format!("{}()$0", name), format!("{}()", name))
+        } else {
+            self = self.trigger_call_info();
+            let snippet = match (ctx.config.add_call_argument_snippets, params) {
+                (true, Params::Named(params)) => {
+                    let function_params_snippet =
+                        params.iter().enumerate().format_with(", ", |(index, param_name), f| {
+                            f(&format_args!("${{{}:{}}}", index + 1, param_name))
+                        });
+                    format!("{}({})$0", name, function_params_snippet)
+                }
+                _ => {
+                    mark::hit!(suppress_arg_snippets);
+                    format!("{}($0)", name)
+                }
+            };
+
+            (snippet, format!("{}(…)", name))
+        };
+        self.lookup_by(name).label(label).insert_snippet(cap, snippet)
+    }
+}