fix: comparison for empty/nil, fixes #321

test/e2e/issues.ts

@@ -87,4 +87,12 @@ describe('Issues', function () {
     const html = await engine.parseAndRender(`{{ name | default: "default name" }}`)
     expect(html).to.equal('default name')
   })
+  it('#321 comparison for empty/nil', async () => {
+    const engine = new Liquid()
+    const html = await engine.parseAndRender(
+      '{% if empty == nil %}true{%else%}false{%endif%}' +
+      '{% if nil == empty %}true{%else%}false{%endif%}'
+    )
+    expect(html).to.equal('falsefalse')
+  })
 })

test/integration/drop/empty-drop.ts

@@ -79,4 +79,14 @@ describe('drop/empty-drop', function () {
     const html = await liquid.parseAndRender(src)
     expect(html).to.equal('true')
   })
+  it('empty != empty', async function () {
+    const src = '{%if empty == empty %}true{%else%}false{% endif %}'
+    const html = await liquid.parseAndRender(src)
+    expect(html).to.equal('false')
+  })
+  it('empty != nil', async function () {
+    const src = '{%if empty == nil %}true{%else%}false{% endif %}'
+    const html = await liquid.parseAndRender(src)
+    expect(html).to.equal('false')
+  })
 })

test/integration/drop/null-drop.ts

@@ -13,22 +13,27 @@ describe('drop/null-drop', function () {
     const html = await liquid.parseAndRender('{{null}}')
     expect(html).to.equal('')
   })
-  it('undefined variable should equal to null', async function () {
+  it('undefined == null', async function () {
     const src = '{%if foo == nil %}foo == nil{%else%}foo != nil{% endif %}'
     const html = await liquid.parseAndRender(src)
     expect(html).to.equal('foo == nil')
   })
-  it('nil equals blank', async function () {
-    const src = '{%if nil == blank %}nil == blank{%else%}nil != blank{% endif %}'
+  it('nil != blank', async function () {
+    const src = '{%if nil == blank %}eq{%else%}neq{% endif %}'
     const html = await liquid.parseAndRender(src)
-    expect(html).to.equal('nil == blank')
+    expect(html).to.equal('neq')
   })
-  it('0 should not equal to null', async function () {
+  it('nil != empty', async function () {
+    const src = '{%if nil == empty %}eq{%else%}neq{% endif %}'
+    const html = await liquid.parseAndRender(src)
+    expect(html).to.equal('neq')
+  })
+  it('0 != null', async function () {
     const src = '{%if 0 == null %}0 == null{%else%}0 != null{% endif %}'
     const html = await liquid.parseAndRender(src)
     expect(html).to.equal('0 != null')
   })
-  it('nil should equal to null', async function () {
+  it('nil == null', async function () {
     const src = '{%if nil == null %}nil == null{%else%}nil != null{% endif %}'
     const html = await liquid.parseAndRender(src)
     expect(html).to.equal('nil == null')