dolphin: Add support for coalesce (#802)

For some reason it's a special case in the AST

Fixes #725

Author: kyleconroy

internal/endtoend/testdata/coalesce/go/db.go renamed to internal/endtoend/testdata/coalesce/mysql/go/db.go

@@ -3,6 +3,7 @@
   "packages": [
     {
       "path": "go",
+      "engine": "mysql",
       "name": "querytest",
       "schema": "query.sql",
       "queries": "query.sql"

internal/endtoend/testdata/coalesce/go/models.go renamed to internal/endtoend/testdata/coalesce/mysql/go/models.go

@@ -0,0 +1,9 @@
+CREATE TABLE foo (bar text, bat text not null);
+
+-- name: Coalesce :many
+SELECT coalesce(bar, '') as login
+FROM foo;
+
+-- name: CoalesceColumns :many
+SELECT bar, bat, coalesce(bar, bat)
+FROM foo;

internal/endtoend/testdata/coalesce/go/query.sql.go renamed to internal/endtoend/testdata/coalesce/mysql/go/query.sql.go

@@ -0,0 +1,12 @@
+{
+  "version": "1",
+  "packages": [
+    {
+      "path": "go",
+      "engine": "postgresql",
+      "name": "querytest",
+      "schema": "query.sql",
+      "queries": "query.sql"
+    }
+  ]
+}

internal/endtoend/testdata/coalesce/query.sql renamed to internal/endtoend/testdata/coalesce/mysql/query.sql

@@ -321,7 +321,7 @@ func (c *cc) convertFieldList(n *pcast.FieldList) *ast.List {
 	return &ast.List{Items: fields}
 }
 
-func (c *cc) convertFuncCallExpr(n *pcast.FuncCallExpr) *ast.FuncCall {
+func (c *cc) convertFuncCallExpr(n *pcast.FuncCallExpr) ast.Node {
 	schema := n.Schema.String()
 	name := strings.ToLower(n.FnName.String())
 
@@ -332,21 +332,28 @@ func (c *cc) convertFuncCallExpr(n *pcast.FuncCallExpr) *ast.FuncCall {
 	}
 	items = append(items, &ast.String{Str: name})
 
-	fn := &ast.FuncCall{
-		Args: &ast.List{},
-		Func: &ast.FuncName{
-			Schema: schema,
-			Name:   name,
-		},
-		Funcname: &ast.List{
-			Items: items,
-		},
-		Location: n.OriginTextPosition(),
-	}
+	args := &ast.List{}
 	for _, arg := range n.Args {
-		fn.Args.Items = append(fn.Args.Items, c.convert(arg))
+		args.Items = append(args.Items, c.convert(arg))
+	}
+
+	if schema == "" && name == "coalesce" {
+		return &ast.CoalesceExpr{
+			Args: args,
+		}
+	} else {
+		return &ast.FuncCall{
+			Args: args,
+			Func: &ast.FuncName{
+				Schema: schema,
+				Name:   name,
+			},
+			Funcname: &ast.List{
+				Items: items,
+			},
+			Location: n.OriginTextPosition(),
+		}
 	}
-	return fn
 }
 
 func (c *cc) convertInsertStmt(n *pcast.InsertStmt) *ast.InsertStmt {