feat: nil/null/empty/blank literals, resolves #102

test/e2e/drop.ts

@@ -0,0 +1,21 @@
+import Liquid from '../..'
+import { expect, use } from 'chai'
+import * as chaiAsPromised from 'chai-as-promised'
+
+use(chaiAsPromised)
+
+describe('drop', function () {
+  var engine: Liquid
+  beforeEach(function () {
+    engine = new Liquid()
+  })
+  it('should test blank strings', async function () {
+    const src = `
+    {% unless settings.fp_heading == blank %}
+        <h1>{{ settings.fp_heading }}</h1>
+    {% endunless %}`
+    var ctx = { settings: { fp_heading: '' } }
+    const html = await engine.parseAndRender(src, ctx)
+    return expect(html).to.match(/^\s+$/)
+  })
+})

test/e2e/parse-and-render.ts

@@ -62,4 +62,9 @@ describe('.parseAndRender()', function () {
     const html = await engine.parseAndRender(src)
     return expect(html).to.equal('apples')
   })
+  it('should support nil(null, undefined) literal', async function () {
+    const src = '{% if notexist == nil %}true{% endif %}'
+    const html = await engine.parseAndRender(src)
+    expect(html).to.equal('true')
+  })
 })

test/unit/builtin/tags/case.ts

@@ -19,22 +19,20 @@ describe('tags/case', function () {
     const html = await liquid.parseAndRender(src)
     return expect(html).to.equal('foo')
   })
-  it('should resolve empty string if not hit', async function () {
-    const src = '{% case empty %}' +
-            '{% when "foo" %}foo{% when ""%}bar' +
-            '{%endcase%}'
-    const ctx = {
-      empty: ''
-    }
-    const html = await liquid.parseAndRender(src, ctx)
+  it('should resolve blank as empty string', async function () {
+    const src = '{% case blank %}{% when ""%}bar{%endcase%}'
+    const html = await liquid.parseAndRender(src)
+    return expect(html).to.equal('bar')
+  })
+  it('should resolve empty as empty string', async function () {
+    const src = '{% case empty %}{% when ""%}bar{%endcase%}'
+    const html = await liquid.parseAndRender(src)
     return expect(html).to.equal('bar')
   })
   it('should accept empty string as branch name', async function () {
-    const src = '{% case false %}' +
-            '{% when "foo" %}foo{% when ""%}bar' +
-            '{%endcase%}'
+    const src = '{% case "" %}{% when ""%}bar{%endcase%}'
     const html = await liquid.parseAndRender(src)
-    return expect(html).to.equal('')
+    return expect(html).to.equal('bar')
   })
   it('should support boolean case', async function () {
     const src = '{% case false %}' +

test/unit/builtin/tags/for.ts

@@ -1,12 +1,12 @@
 import Liquid from 'src/liquid'
 import { expect, use } from 'chai'
 import * as chaiAsPromised from 'chai-as-promised'
-import IContext from 'src/scope/icontext'
+import { Context } from 'src/scope/scope'
 
 use(chaiAsPromised)
 
 describe('tags/for', function () {
-  let liquid: Liquid, ctx: IContext
+  let liquid: Liquid, ctx: Context
   before(function () {
     liquid = new Liquid()
     liquid.registerTag('throwingTag', {

test/unit/drop/blank-drop.ts

@@ -0,0 +1,52 @@
+import { expect } from 'chai'
+import Liquid from 'src/liquid'
+
+describe('drop/blank-drop', function () {
+  let liquid: Liquid
+  before(() => (liquid = new Liquid()))
+
+  it('render blank drop as blank string', async function () {
+    const html = await liquid.parseAndRender('{{blank}}')
+    expect(html).to.equal('')
+  })
+  it('blank equals nil', async function () {
+    const src = '{%if blank == nil %}blank == nil{%else%}blank != nil{% endif %}'
+    const html = await liquid.parseAndRender(src)
+    expect(html).to.equal('blank == nil')
+  })
+  it('false is blank', async function () {
+    const src = '{%if false == blank %}false == blank{%else%}false != blank{% endif %}'
+    const html = await liquid.parseAndRender(src)
+    expect(html).to.equal('false == blank')
+  })
+  it('"" is blank', async function () {
+    const src = '{%if "" == blank %}"" == blank{%else%}"" != blank{% endif %}'
+    const html = await liquid.parseAndRender(src)
+    expect(html).to.equal('"" == blank')
+  })
+  it('"  " is blank', async function () {
+    const src = '{%if "  " == blank %}"  " == blank{%else%}"  " != blank{% endif %}'
+    const html = await liquid.parseAndRender(src)
+    expect(html).to.equal('"  " == blank')
+  })
+  it('{} is blank', async function () {
+    const src = '{%if obj == blank %}{} == blank{%else%}{} != blank{% endif %}'
+    const html = await liquid.parseAndRender(src, { obj: {} })
+    expect(html).to.equal('{} == blank')
+  })
+  it('{foo: 1} is not blank', async function () {
+    const src = '{%if obj == blank %}{foo: 1} == blank{%else%}{foo: 1} != blank{% endif %}'
+    const html = await liquid.parseAndRender(src, { obj: { foo: 1 } })
+    expect(html).to.equal('{foo: 1} != blank')
+  })
+  it('[] is blank', async function () {
+    const src = '{%if arr == blank %}[] == blank{%else%}[] != blank{% endif %}'
+    const html = await liquid.parseAndRender(src, { arr: [] })
+    expect(html).to.equal('[] == blank')
+  })
+  it('[1] is not blank', async function () {
+    const src = '{%if arr == blank %}[1] == blank{%else%}[1] != blank{% endif %}'
+    const html = await liquid.parseAndRender(src, { arr: [1] })
+    expect(html).to.equal('[1] != blank')
+  })
+})

test/unit/drop/empty-drop.ts

@@ -0,0 +1,52 @@
+import { expect } from 'chai'
+import Liquid from 'src/liquid'
+
+describe('drop/empty-drop', function () {
+  let liquid: Liquid
+  before(() => (liquid = new Liquid()))
+
+  it('render empty drop as empty string', async function () {
+    const html = await liquid.parseAndRender('{{empty}}')
+    expect(html).to.equal('')
+  })
+  it('nil is not empty', async function () {
+    const src = '{%if nil == empty %}nil == empty{%else%}nil != empty{% endif %}'
+    const html = await liquid.parseAndRender(src)
+    expect(html).to.equal('nil != empty')
+  })
+  it('false is not empty', async function () {
+    const src = '{%if false == empty %}false == empty{%else%}false != empty{% endif %}'
+    const html = await liquid.parseAndRender(src)
+    expect(html).to.equal('false != empty')
+  })
+  it('"" is empty', async function () {
+    const src = '{%if "" == empty %}"" == empty{%else%}"" != empty{% endif %}'
+    const html = await liquid.parseAndRender(src)
+    expect(html).to.equal('"" == empty')
+  })
+  it('"  " is not empty', async function () {
+    const src = '{%if "  " == empty %}"  " == empty{%else%}"  " != empty{% endif %}'
+    const html = await liquid.parseAndRender(src)
+    expect(html).to.equal('"  " != empty')
+  })
+  it('{} is empty', async function () {
+    const src = '{%if obj == empty %}{} == empty{%else%}{} != empty{% endif %}'
+    const html = await liquid.parseAndRender(src, { obj: {} })
+    expect(html).to.equal('{} == empty')
+  })
+  it('{foo: 1} is not empty', async function () {
+    const src = '{%if obj == empty %}{foo: 1} == empty{%else%}{foo: 1} != empty{% endif %}'
+    const html = await liquid.parseAndRender(src, { obj: { foo: 1 } })
+    expect(html).to.equal('{foo: 1} != empty')
+  })
+  it('[] is empty', async function () {
+    const src = '{%if arr == empty %}[] == empty{%else%}[] != empty{% endif %}'
+    const html = await liquid.parseAndRender(src, { arr: [] })
+    expect(html).to.equal('[] == empty')
+  })
+  it('[1] is not empty', async function () {
+    const src = '{%if arr == empty %}[1] == empty{%else%}[1] != empty{% endif %}'
+    const html = await liquid.parseAndRender(src, { arr: [1] })
+    expect(html).to.equal('[1] != empty')
+  })
+})

test/unit/drop/null-drop.ts

@@ -0,0 +1,36 @@
+import { expect } from 'chai'
+import Liquid from 'src/liquid'
+
+describe('drop/null-drop', function () {
+  let liquid: Liquid
+  before(() => (liquid = new Liquid()))
+
+  it('render nil as empty string', async function () {
+    const html = await liquid.parseAndRender('{{nil}}')
+    expect(html).to.equal('')
+  })
+  it('render null as empty string', async function () {
+    const html = await liquid.parseAndRender('{{null}}')
+    expect(html).to.equal('')
+  })
+  it('undefined variable should equal to 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 %}'
+    const html = await liquid.parseAndRender(src)
+    expect(html).to.equal('nil == blank')
+  })
+  it('0 should not equal to 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 () {
+    const src = '{%if nil == null %}nil == null{%else%}nil != null{% endif %}'
+    const html = await liquid.parseAndRender(src)
+    expect(html).to.equal('nil == null')
+  })
+})

test/unit/render/syntax.ts

@@ -2,7 +2,7 @@ import Scope from 'src/scope/scope'
 import { expect } from 'chai'
 import { evalExp, evalValue, isTruthy } from 'src/render/syntax'
 
-describe('expression', function () {
+describe('render/syntax', function () {
   let scope: Scope
 
   beforeEach(function () {
@@ -29,10 +29,16 @@ describe('expression', function () {
       expect(evalValue('-23.', scope)).to.equal(-23)
       expect(evalValue('23', scope)).to.equal(23)
     })
-    it('should eval literal', function () {
+    it('should eval string literal', function () {
       expect(evalValue('"ab\'c"', scope)).to.equal("ab'c")
       expect(evalValue("'ab\"c'", scope)).to.equal('ab"c')
     })
+    it('should eval nil literal', function () {
+      expect(evalValue('nil', scope)).to.be.null
+    })
+    it('should eval null literal', function () {
+      expect(evalValue('null', scope)).to.be.null
+    })
     it('should eval scope variables', function () {
       expect(evalValue('one', scope)).to.equal(1)
       expect(evalValue('has_value?', scope)).to.equal(true)

test/unit/scope/scope.ts

@@ -1,11 +1,10 @@
 import * as chai from 'chai'
-import Scope from 'src/scope/scope'
-import IContext from 'src/scope/icontext'
+import Scope, { Context } from 'src/scope/scope'
 
 const expect = chai.expect
 
 describe('scope', function () {
-  let scope: Scope, ctx: IContext
+  let scope: Scope, ctx: Context
   beforeEach(function () {
     ctx = {
       foo: 'zoo',
@@ -64,7 +63,7 @@ describe('scope', function () {
       expect(scope.get('foo')).equal('zoo')
     })
 
-    it('should get undefined property', function () {
+    it('undefined property should yield undefined', function () {
       function fn () {
         scope.get('notdefined')
       }