Treat if merge with false string as false (#4569)

libs/ui/src/context/merge.spec.ts

@@ -563,6 +563,51 @@ const mergeFormulaTestCases: MergeWithContextTestCase[] = [
   },
 ]
 
+const mergeIfTestCases: MergeWithContextTestCase[] = [
+  {
+    name: "simple if statement true",
+    context: new Context(),
+    input: "$If{[true][a][b]}",
+    expected: "a",
+  },
+  {
+    name: "simple if statement false",
+    context: new Context(),
+    input: "$If{[false][a][b]}",
+    expected: "b",
+  },
+  {
+    name: "if with context value present",
+    context: new Context().addRecordDataFrame({
+      foo: "A value",
+    }),
+    input: "$If{[${foo}][a][b]}",
+    expected: "a",
+  },
+  {
+    name: "if with context value empty string",
+    context: new Context().addRecordDataFrame({
+      foo: "",
+    }),
+    input: "$If{[${foo}][a][b]}",
+    expected: "b",
+  },
+  {
+    name: "if with context value missing",
+    context: new Context().addRecordDataFrame({}),
+    input: "$If{[${foo}][a][b]}",
+    expected: "b",
+  },
+  {
+    name: "if with context value false string",
+    context: new Context().addRecordDataFrame({
+      foo: "false",
+    }),
+    input: "$If{[${foo}][a][b]}",
+    expected: "b",
+  },
+]
+
 describe("merge", () => {
   describe("$SignalOutput context", () => {
     signalOutputMergeTestCases.forEach((tc) => {
@@ -679,4 +724,12 @@ describe("merge", () => {
       })
     })
   })
+
+  describe("mergeIf", () => {
+    mergeIfTestCases.forEach((tc) => {
+      test(tc.name, () => {
+        expect(tc.context.merge(tc.input, tc.options)).toEqual(tc.expected)
+      })
+    })
+  })
 })

libs/ui/src/context/merge.ts

@@ -250,7 +250,8 @@ const handlers: Record<MergeType, MergeHandler> = {
     } catch {
       throw InvalidIfMergeMsg
     }
-    return context.merge(parts[0])
+    const conditionResult = context.merge(parts[0])
+    return conditionResult && conditionResult !== "false"
       ? context.merge(parts[1])
       : context.merge(parts[2])
   },