add + operator overloading to clause to OR join two clauses

Author: leafo

lapis/db/base.lua

@@ -3,6 +3,7 @@ do
   local _obj_0 = _G
   setmetatable, getmetatable, tostring = _obj_0.setmetatable, _obj_0.getmetatable, _obj_0.tostring
 end
+local clause, is_clause
 local DBRaw
 do
   local _class_0
@@ -73,6 +74,15 @@ do
         return opts.operator
       end
       return "AND"
+    end,
+    __add = function(self, other)
+      assert(is_clause(other), "db.clause.__add: right operand must be a clause object")
+      return clause({
+        self,
+        other
+      }, {
+        operator = "OR"
+      })
     end
   }
   _base_0.__index = _base_0
@@ -91,15 +101,13 @@ do
   _base_0.__class = _class_0
   DBClause = _class_0
 end
-local clause
 clause = function(clause, opts)
   assert(not getmetatable(clause), "db.clause: attempted to create clause from object that has metatable")
   return setmetatable({
     clause,
     opts
   }, DBClause.__base)
 end
-local is_clause
 is_clause = function(val)
   return getmetatable(val) == DBClause.__base
 end

lapis/db/base.moon

@@ -1,6 +1,8 @@
 
 import setmetatable, getmetatable, tostring from _G
 
+local clause, is_clause
+
 class DBRaw
 raw = (val) -> setmetatable {tostring val}, DBRaw.__base
 is_raw = (val) -> getmetatable(val) == DBRaw.__base
@@ -18,6 +20,10 @@ class DBClause
 
     "AND"
 
+  __add: (other) =>
+    assert is_clause(other), "db.clause.__add: right operand must be a clause object"
+    clause { @, other }, operator: "OR"
+
 clause = (clause, opts) ->
   assert not getmetatable(clause), "db.clause: attempted to create clause from object that has metatable"
   setmetatable {clause, opts}, DBClause.__base

spec/postgres_spec.moon

@@ -920,6 +920,60 @@ describe "lapis.db.postgres", ->
         "db.encode_clause: passed an empty clause (use allow_empty: true to permit empty clause)"
       )
 
+    describe "+ operator", ->
+      it "combines two clauses with OR", ->
+        a = db.clause hello: "world"
+        b = db.clause { "not deleted" }
+        combined = a + b
+        assert.same '("hello" = \'world\') OR ((not deleted))', db.encode_clause combined
+
+      it "chains multiple clauses", ->
+        a = db.clause { "a" }
+        b = db.clause { "b" }
+        c = db.clause { "c" }
+        combined = a + b + c
+        assert.same '((a)) OR ((b)) OR ((c))', db.encode_clause combined
+
+      it "works with db.raw and db.NULL in clauses", ->
+        a = db.clause { status: db.raw "active" }
+        b = db.clause { deleted: db.NULL }
+        combined = a + b
+        assert.same '("status" = active) OR ("deleted" IS NULL)', db.encode_clause combined
+
+      it "works with db.list in clauses", ->
+        a = db.clause { id: db.list {1, 2, 3} }
+        b = db.clause { "archived" }
+        combined = a + b
+        assert.same '("id" IN (1, 2, 3)) OR ((archived))', db.encode_clause combined
+
+      it "errors when right operand is a plain table", ->
+        a = db.clause hello: "world"
+        assert.has_error(
+          -> a + { hello: "world" }
+          "db.clause.__add: right operand must be a clause object"
+        )
+
+      it "errors when right operand is a string", ->
+        a = db.clause hello: "world"
+        assert.has_error(
+          -> a + "not a clause"
+          "db.clause.__add: right operand must be a clause object"
+        )
+
+      it "errors when right operand is a number", ->
+        a = db.clause hello: "world"
+        assert.has_error(
+          -> a + 123
+          "db.clause.__add: right operand must be a clause object"
+        )
+
+      it "errors when right operand is nil", ->
+        a = db.clause hello: "world"
+        assert.has_error(
+          -> a + nil
+          "db.clause.__add: right operand must be a clause object"
+        )
+
   describe "encode_assigns", ->
     it "writes output to buffer", ->
       buffer = {"hello"}