From 5d6b2337f8f2867ae420d7d33993335841216e63 Mon Sep 17 00:00:00 2001
From: Gabriel Nordeborn <gabbe.nord@gmail.com>
Date: Wed, 11 Jan 2023 19:49:21 +0100
Subject: [PATCH 1/3] let ppat_any trigger completion in patterns. better
 ergonomics

---
 analysis/src/CompletionFrontEnd.ml            |  3 +-
 analysis/tests/src/CompletionPattern.res      |  3 ++
 .../src/expected/CompletionPattern.res.txt    | 33 +++++++++++++++++++
 3 files changed, 38 insertions(+), 1 deletion(-)

diff --git a/analysis/src/CompletionFrontEnd.ml b/analysis/src/CompletionFrontEnd.ml
index d42f8f448..9aa9146ba 100644
--- a/analysis/src/CompletionFrontEnd.ml
+++ b/analysis/src/CompletionFrontEnd.ml
@@ -681,7 +681,7 @@ let completionWithParser1 ~currentFile ~debug ~offset ~path ~posCursor ~text =
       if locHasCursor pat.Parsetree.ppat_loc then Some v else None
     in
     match pat.ppat_desc with
-    | Ppat_any | Ppat_constant _ | Ppat_interval _ -> None
+    | Ppat_constant _ | Ppat_interval _ -> None
     | Ppat_lazy p
     | Ppat_constraint (p, _)
     | Ppat_alias (p, _)
@@ -695,6 +695,7 @@ let completionWithParser1 ~currentFile ~debug ~offset ~path ~posCursor ~text =
       match orPatWithItem with
       | None when isPatternHole p1 || isPatternHole p2 -> Some ("", patternPath)
       | v -> v)
+    | Ppat_any -> someIfHasCursor ("", patternPath)
     | Ppat_var {txt} -> someIfHasCursor (txt, patternPath)
     | Ppat_construct ({txt = Lident "()"}, None) ->
       (* switch s { | (<com>) }*)
diff --git a/analysis/tests/src/CompletionPattern.res b/analysis/tests/src/CompletionPattern.res
index 26cba1167..749569099 100644
--- a/analysis/tests/src/CompletionPattern.res
+++ b/analysis/tests/src/CompletionPattern.res
@@ -191,3 +191,6 @@ let s = (true, Some(true), [false])
 
 // switch b { | #one | #three({test: true}, true | )  }
 //                                                ^com
+
+// switch s { | (true, _, []) }
+//                      ^com
diff --git a/analysis/tests/src/expected/CompletionPattern.res.txt b/analysis/tests/src/expected/CompletionPattern.res.txt
index a1e346ef3..8aef02425 100644
--- a/analysis/tests/src/expected/CompletionPattern.res.txt
+++ b/analysis/tests/src/expected/CompletionPattern.res.txt
@@ -871,3 +871,36 @@ Completable: Cpattern Value[b]->polyvariantPayload::three($1)
     "documentation": null
   }]
 
+Complete src/CompletionPattern.res 194:24
+posCursor:[194:24] posNoWhite:[194:23] Found expr:[194:3->194:31]
+posCursor:[194:24] posNoWhite:[194:23] Found pattern:[194:16->194:29]
+posCursor:[194:24] posNoWhite:[194:23] Found pattern:[194:23->194:24]
+Completable: Cpattern Value[s]->tuple($1)
+[{
+    "label": "None",
+    "kind": 4,
+    "tags": [],
+    "detail": "bool",
+    "documentation": null
+  }, {
+    "label": "Some(_)",
+    "kind": 4,
+    "tags": [],
+    "detail": "bool",
+    "documentation": null,
+    "insertText": "Some(${1:_})",
+    "insertTextFormat": 2
+  }, {
+    "label": "Some(true)",
+    "kind": 4,
+    "tags": [],
+    "detail": "bool",
+    "documentation": null
+  }, {
+    "label": "Some(false)",
+    "kind": 4,
+    "tags": [],
+    "detail": "bool",
+    "documentation": null
+  }]
+

From 17f0ee7f267d4eb00416d87d5050a958ee377520 Mon Sep 17 00:00:00 2001
From: Gabriel Nordeborn <gabbe.nord@gmail.com>
Date: Wed, 11 Jan 2023 19:53:18 +0100
Subject: [PATCH 2/3] changelog

---
 CHANGELOG.md | 1 +
 1 file changed, 1 insertion(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index a054d487c..1d69e3756 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -24,6 +24,7 @@
 - Complete for `React.element` creator functions (`React.string` etc) when in JSX context. https://github.com/rescript-lang/rescript-vscode/pull/681
 - Handle optional record fields in expression/pattern completion. https://github.com/rescript-lang/rescript-vscode/pull/691
 - Expand options in completion to make working with options a bit more ergonomic. https://github.com/rescript-lang/rescript-vscode/pull/690
+- Let `_` trigger completion in patterns. https://github.com/rescript-lang/rescript-vscode/pull/692
 
 #### :nail_care: Polish
 

From b8ae91d72cb4f11ff389ba5c8f1e3d62c7be9931 Mon Sep 17 00:00:00 2001
From: Gabriel Nordeborn <gabbe.nord@gmail.com>
Date: Thu, 12 Jan 2023 20:23:20 +0100
Subject: [PATCH 3/3] comment

---
 analysis/src/CompletionFrontEnd.ml | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/analysis/src/CompletionFrontEnd.ml b/analysis/src/CompletionFrontEnd.ml
index 9aa9146ba..60f67658e 100644
--- a/analysis/src/CompletionFrontEnd.ml
+++ b/analysis/src/CompletionFrontEnd.ml
@@ -695,7 +695,12 @@ let completionWithParser1 ~currentFile ~debug ~offset ~path ~posCursor ~text =
       match orPatWithItem with
       | None when isPatternHole p1 || isPatternHole p2 -> Some ("", patternPath)
       | v -> v)
-    | Ppat_any -> someIfHasCursor ("", patternPath)
+    | Ppat_any ->
+      (* We treat any `_` as an empty completion. This is mainly because we're
+         inserting `_` in snippets and automatically put the cursor there. So
+         letting it trigger an empty completion improves the ergonomics by a
+         lot. *)
+      someIfHasCursor ("", patternPath)
     | Ppat_var {txt} -> someIfHasCursor (txt, patternPath)
     | Ppat_construct ({txt = Lident "()"}, None) ->
       (* switch s { | (<com>) }*)