feat(lsp): Implement `textDocument/signatureHelp` (#9330)

Co-authored-by: Kitson Kelly <me@kitsonkelly.com>

4 files changed, 70 insertions, 0 deletions

diff --git a/cli/tests/lsp/signature_help_did_change_notification.json b/cli/tests/lsp/signature_help_did_change_notification.json
new file mode 100644
index 000000000..f88eaa9ff
--- /dev/null
+++ b/cli/tests/lsp/signature_help_did_change_notification.json
@@ -0,0 +1,25 @@
+{
+  "jsonrpc": "2.0",
+  "method": "textDocument/didChange",
+  "params": {
+    "textDocument": {
+      "uri": "file:///a/file.ts",
+      "version": 2
+    },
+    "contentChanges": [
+      {
+        "range": {
+          "start": {
+            "line": 9,
+            "character": 4
+          },
+          "end": {
+            "line": 9,
+            "character": 4
+          }
+        },
+        "text": "123, "
+      }
+    ]
+  }
+}
diff --git a/cli/tests/lsp/signature_help_did_open_notification.json b/cli/tests/lsp/signature_help_did_open_notification.json
new file mode 100644
index 000000000..1ba1f7586
--- /dev/null
+++ b/cli/tests/lsp/signature_help_did_open_notification.json
@@ -0,0 +1,12 @@
+{
+  "jsonrpc": "2.0",
+  "method": "textDocument/didOpen",
+  "params": {
+    "textDocument": {
+      "uri": "file:///a/file.ts",
+      "languageId": "typescript",
+      "version": 1,
+      "text": "/**\n * Adds two numbers.\n * @param a This is a first number.\n * @param b This is a second number.\n */\nfunction add(a: number, b: number) {\n  return a + b;\n}\n\nadd("
+    }
+  }
+}
diff --git a/cli/tests/lsp/signature_help_request_01.json b/cli/tests/lsp/signature_help_request_01.json
new file mode 100644
index 000000000..c3e185e08
--- /dev/null
+++ b/cli/tests/lsp/signature_help_request_01.json
@@ -0,0 +1,19 @@
+{
+  "jsonrpc": "2.0",
+  "id": 1,
+  "method": "textDocument/signatureHelp",
+  "params": {
+    "textDocument": {
+      "uri": "file:///a/file.ts"
+    },
+    "position": {
+      "character": 4,
+      "line": 9
+    },
+    "context": {
+      "triggerKind": 2,
+      "triggerCharacter": "(",
+      "isRetrigger": false
+    }
+  }
+}
diff --git a/cli/tests/lsp/signature_help_request_02.json b/cli/tests/lsp/signature_help_request_02.json
new file mode 100644
index 000000000..c2a6e0abb
--- /dev/null
+++ b/cli/tests/lsp/signature_help_request_02.json
@@ -0,0 +1,14 @@
+{
+  "id": 2,
+  "jsonrpc": "2.0",
+  "method": "textDocument/signatureHelp",
+  "params": {
+    "textDocument": {
+      "uri": "file:///a/file.ts"
+    },
+    "position": {
+      "character": 8,
+      "line": 9
+    }
+  }
+}