test: Add tests for computed elements (#787)

Co-authored-by: Johannes Vogel <31311694+johannes-vogel@users.noreply.github.com>

db-service/lib/cqn4sql.js

@@ -530,7 +530,7 @@ function cqn4sql(originalQuery, model) {
       res = getTransformedTokenStream([value], baseLink)[0]
     } else if (xpr) {
       res = { xpr: getTransformedTokenStream(value.xpr, baseLink) }
-    } else if (val) {
+    } else if (val !== undefined) {
       res = { val }
     } else if (func) {
       res = { args: getTransformedFunctionArgs(value.args, baseLink), func: value.func }

test/compliance/resources/db/complex/computed.cds

@@ -0,0 +1,30 @@
+namespace complex.computed;
+
+entity static {
+  value   : Integer;
+  integer : Integer = 1;
+  double  : Double  = 0.1;
+  string  : String  = '';
+}
+
+entity dynamic {
+  integer : Integer;
+  @(Core.Computed: true,readonly)
+  ![case] : String = (
+    case
+      when
+        integer = 0
+      then
+        'zero'
+      when
+        integer = 1
+      then
+        'one'
+      when
+        integer = 2
+      then
+        'two'
+    end
+  );
+  lambda  : String = (integer = 0 ? 'none' : 'some')
+}

test/compliance/resources/db/complex/computed/complex.computed.dynamic.js

@@ -0,0 +1,17 @@
+module.exports = [
+  {
+    integer: 0,
+    '=case': 'zero',
+    '=lambda': 'none',
+  },
+  {
+    integer: 1,
+    '=case': 'one',
+    '=lambda': 'some',
+  },
+  {
+    integer: 2,
+    '=case': 'two',
+    '=lambda': 'some',
+  }
+]

test/compliance/resources/db/complex/computed/complex.computed.static.js

@@ -0,0 +1,7 @@
+module.exports = [
+  {
+    '=integer': 1,
+    '=double': 0.1,
+    '=string': '',
+  }
+]

test/compliance/resources/db/complex/index.cds

@@ -1,4 +1,5 @@
 namespace complex;
 
+using from './computed';
 using from './associations';
 using from './associationsUnmanaged';