feat: Add support of inner expressions enclosed by parentheses

src/liquid-options.ts

@@ -84,6 +84,8 @@ export interface LiquidOptions {
   operators?: Operators;
   /** Respect parameter order when using filters like "for ... reversed limit", Defaults to `false`. */
   orderedFilterParameters?: boolean;
+  /** Allow parenthesized expressions as operands in conditions and loops, e.g. `{% if (foo | upcase) == "BAR" %}`. This is a non-standard extension to Liquid. Defaults to `false`. */
+  groupedExpressions?: boolean;
   /** For DoS handling, limit total length of templates parsed in one `parse()` call. A typical PC can handle 1e8 (100M) characters without issues. */
   parseLimit?: number;
   /** For DoS handling, limit total time (in ms) for each `render()` call. */
@@ -159,6 +161,7 @@ export interface NormalizedFullOptions extends NormalizedOptions {
   globals: object;
   keepOutputType: boolean;
   operators: Operators;
+  groupedExpressions: boolean;
   parseLimit: number;
   renderLimit: number;
   memoryLimit: number;
@@ -195,6 +198,7 @@ export const defaultOptions: NormalizedFullOptions = {
   globals: {},
   keepOutputType: false,
   operators: defaultOperators,
+  groupedExpressions: false,
   memoryLimit: Infinity,
   parseLimit: Infinity,
   renderLimit: Infinity

src/parser/parser.ts

@@ -28,7 +28,7 @@ export class Parser {
   public parse (html: string, filepath?: string): Template[] {
     html = String(html)
     this.parseLimit.use(html.length)
-    const tokenizer = new Tokenizer(html, this.liquid.options.operators, filepath)
+    const tokenizer = new Tokenizer(html, this.liquid.options.operators, filepath, undefined, this.liquid.options.groupedExpressions)
     const tokens = tokenizer.readTopLevelTokens(this.liquid.options)
     return this.parseTokens(tokens)
   }

src/parser/token-kind.ts

@@ -12,5 +12,6 @@ export enum TokenKind {
   Quoted = 1024,
   Operator = 2048,
   FilteredValue = 4096,
+  GroupedExpression = 8192,
   Delimited = Tag | Output
 }

src/parser/tokenizer.spec.ts

@@ -1,4 +1,4 @@
-import { LiquidTagToken, HTMLToken, QuotedToken, OutputToken, TagToken, OperatorToken, RangeToken, PropertyAccessToken, NumberToken, IdentifierToken } from '../tokens'
+import { LiquidTagToken, HTMLToken, QuotedToken, OutputToken, TagToken, OperatorToken, RangeToken, PropertyAccessToken, NumberToken, IdentifierToken, GroupedExpressionToken } from '../tokens'
 import { Tokenizer } from './tokenizer'
 import { defaultOperators } from '../render/operator'
 import { createTrie } from '../util/operator-trie'
@@ -247,6 +247,58 @@ describe('Tokenizer', function () {
       expect(range!.getText()).toEqual('(a.b..c["..d"])')
     })
   })
+  describe('#readGroupedExpression()', () => {
+    function createGrouped (input: string): Tokenizer {
+      const t = new Tokenizer(input, defaultOperators)
+      t.groupedExpressions = true
+      return t
+    }
+    it('should read `(foo | upcase)` as GroupedExpressionToken', () => {
+      const token = createGrouped('(foo | upcase)').readValue()
+      expect(token).toBeInstanceOf(GroupedExpressionToken)
+      const grouped = token as GroupedExpressionToken
+      expect(grouped.getText()).toBe('(foo | upcase)')
+      expect(grouped.initial.postfix).toHaveLength(1)
+      expect(grouped.filters).toHaveLength(1)
+      expect(grouped.filters[0].name).toBe('upcase')
+    })
+    it('should read `(foo | append: "!")` with filter argument', () => {
+      const token = createGrouped('(foo | append: "!")').readValue()
+      expect(token).toBeInstanceOf(GroupedExpressionToken)
+      const grouped = token as GroupedExpressionToken
+      expect(grouped.filters).toHaveLength(1)
+      expect(grouped.filters[0].name).toBe('append')
+      expect(grouped.filters[0].args).toHaveLength(1)
+    })
+    it('should read nested `((foo | append: "!") | upcase)`', () => {
+      const token = createGrouped('((foo | append: "!") | upcase)').readValue()
+      expect(token).toBeInstanceOf(GroupedExpressionToken)
+      const grouped = token as GroupedExpressionToken
+      expect(grouped.filters).toHaveLength(1)
+      expect(grouped.filters[0].name).toBe('upcase')
+      expect(grouped.initial.postfix).toHaveLength(1)
+      expect(grouped.initial.postfix[0]).toBeInstanceOf(GroupedExpressionToken)
+    })
+    it('should parse `(a | upcase) == "BAR"` as expression', () => {
+      const exp = [...createGrouped('(a | upcase) == "BAR"').readExpressionTokens()]
+      expect(exp).toHaveLength(3)
+      expect(exp[0]).toBeInstanceOf(GroupedExpressionToken)
+      expect(exp[1]).toBeInstanceOf(OperatorToken)
+      expect(exp[1].getText()).toBe('==')
+      expect(exp[2]).toBeInstanceOf(QuotedToken)
+    })
+    it('should still parse `(1..3)` as RangeToken', () => {
+      const token = createGrouped('(1..3)').readValue()
+      expect(token).toBeInstanceOf(RangeToken)
+    })
+    it('should return undefined for unclosed parens', () => {
+      const token = createGrouped('(foo | upcase').readValue()
+      expect(token).toBeUndefined()
+    })
+    it('should fall back to readRange when flag is off', () => {
+      expect(() => new Tokenizer('(foo | upcase)', defaultOperators).readValue()).toThrow('invalid range syntax')
+    })
+  })
   describe('#readFilter()', () => {
     it('should read a simple filter', function () {
       const tokenizer = new Tokenizer('| plus')

src/parser/tokenizer.ts

@@ -1,4 +1,4 @@
-import { FilteredValueToken, TagToken, HTMLToken, HashToken, QuotedToken, LiquidTagToken, OutputToken, ValueToken, Token, RangeToken, FilterToken, TopLevelToken, PropertyAccessToken, OperatorToken, LiteralToken, IdentifierToken, NumberToken } from '../tokens'
+import { FilteredValueToken, TagToken, HTMLToken, HashToken, QuotedToken, LiquidTagToken, OutputToken, ValueToken, Token, RangeToken, FilterToken, TopLevelToken, PropertyAccessToken, OperatorToken, LiteralToken, IdentifierToken, NumberToken, GroupedExpressionToken } from '../tokens'
 import { OperatorHandler } from '../render/operator'
 import { TrieNode, LiteralValue, Trie, createTrie, ellipsis, literalValues, TokenizationError, TYPES, QUOTE, BLANK, NUMBER, SIGN, isWord, isString } from '../util'
 import { Operators, Expression } from '../render'
@@ -9,6 +9,7 @@ import { whiteSpaceCtrl } from './whitespace-ctrl'
 export class Tokenizer {
   p: number
   N: number
+  public groupedExpressions: boolean
   private rawBeginAt = -1
   private opTrie: Trie<OperatorHandler>
   private literalTrie: Trie<LiteralValue>
@@ -17,12 +18,14 @@ export class Tokenizer {
     public input: string,
     operators: Operators = defaultOptions.operators,
     public file?: string,
-    range?: [number, number]
+    range?: [number, number],
+    groupedExpressions = false
   ) {
     this.p = range ? range[0] : 0
     this.N = range ? range[1] : input.length
     this.opTrie = createTrie(operators)
     this.literalTrie = createTrie(literalValues)
+    this.groupedExpressions = groupedExpressions
   }
 
   readExpression () {
@@ -310,7 +313,15 @@ export class Tokenizer {
   readValue (): ValueToken | undefined {
     this.skipBlank()
     const begin = this.p
-    const variable = this.readLiteral() || this.readQuoted() || this.readRange() || this.readNumber()
+    let variable: ValueToken | undefined = this.readLiteral() || this.readQuoted()
+    if (!variable && this.peek() === '(') {
+      if (this.groupedExpressions && !this.looksLikeRange()) {
+        variable = this.readGroupedExpression()
+      } else {
+        variable = this.readRange()
+      }
+    }
+    variable = variable || this.readNumber()
     const props = this.readProperties(!variable)
     if (!props.length) return variable
     return new PropertyAccessToken(variable, props, this.input, begin, this.p)
@@ -420,6 +431,70 @@ export class Tokenizer {
     return new QuotedToken(this.input, begin, this.p, this.file)
   }
 
+  readGroupedExpression (): GroupedExpressionToken | undefined {
+    this.skipBlank()
+    if (this.peek() !== '(') return
+    const begin = this.p
+    ++this.p
+    const closeParen = this.findMatchingParen()
+    if (closeParen === -1) {
+      this.p = begin
+      return
+    }
+    const savedN = this.N
+    this.N = closeParen
+    const fvt = this.readFilteredValue()
+    this.N = savedN
+    this.p = closeParen + 1
+    return new GroupedExpressionToken(fvt.initial, fvt.filters, this.input, begin, this.p, this.file)
+  }
+
+  private findMatchingParen (): number {
+    let depth = 1
+    let i = this.p
+    while (i < this.N && depth > 0) {
+      const ch = this.input[i]
+      if (ch === '(') {
+        depth++
+      } else if (ch === ')') {
+        depth--
+        if (depth === 0) return i
+      } else if (ch === '"' || ch === "'") {
+        const quote = ch
+        i++
+        while (i < this.N && this.input[i] !== quote) {
+          if (this.input[i] === '\\') i++
+          i++
+        }
+      }
+      i++
+    }
+    return -1
+  }
+
+  private looksLikeRange (): boolean {
+    let i = this.p + 1
+    let depth = 1
+    while (i < this.N && depth > 0) {
+      const ch = this.input[i]
+      if (ch === '(') {
+        depth++
+      } else if (ch === ')') {
+        depth--
+      } else if (ch === '"' || ch === "'") {
+        i++
+        while (i < this.N && this.input[i] !== ch) {
+          if (this.input[i] === '\\') i++
+          i++
+        }
+      } else if (depth === 1 && ch === '.' && this.input[i + 1] === '.') {
+        return true
+      }
+      i++
+    }
+    return false
+  }
+
   * readFileNameTemplate (options: NormalizedFullOptions): IterableIterator<TopLevelToken> {
     const { outputDelimiterLeft } = options
     const htmlStopStrings = [',', ' ', '\r', '\n', '\t', outputDelimiterLeft]

src/render/expression.ts

@@ -1,5 +1,5 @@
-import { QuotedToken, RangeToken, OperatorToken, Token, PropertyAccessToken, OperatorType, operatorTypes } from '../tokens'
-import { isRangeToken, isPropertyAccessToken, UndefinedVariableError, range, isOperatorToken, assert } from '../util'
+import { QuotedToken, RangeToken, OperatorToken, Token, PropertyAccessToken, OperatorType, operatorTypes, GroupedExpressionToken } from '../tokens'
+import { isRangeToken, isPropertyAccessToken, isGroupedExpressionToken, UndefinedVariableError, range, isOperatorToken, assert } from '../util'
 import type { Context } from '../context'
 import type { UnaryOperatorHandler } from '../render'
 import { Drop } from '../drop'
@@ -40,6 +40,12 @@ export function * evalToken (token: Token | undefined, ctx: Context, lenient = f
   if ('content' in token) return token.content
   if (isPropertyAccessToken(token)) return yield evalPropertyAccessToken(token, ctx, lenient)
   if (isRangeToken(token)) return yield evalRangeToken(token, ctx)
+  if (isGroupedExpressionToken(token)) return yield evalGroupedExpressionToken(token, ctx, lenient)
+}
+
+function * evalGroupedExpressionToken (token: GroupedExpressionToken, ctx: Context, lenient: boolean): IterableIterator<unknown> {
+  assert(token.resolvedValue, 'grouped expression not resolved')
+  return yield token.resolvedValue!.value(ctx, lenient)
 }
 
 function * evalPropertyAccessToken (token: PropertyAccessToken, ctx: Context, lenient: boolean): IterableIterator<unknown> {

src/tags/case.ts

@@ -1,7 +1,7 @@
 import { ValueToken, Liquid, toValue, evalToken, Value, Emitter, TagToken, TopLevelToken, Context, Template, Tag, ParseStream } from '..'
 import { Parser } from '../parser'
 import { equals } from '../render'
-import { Arguments } from '../template'
+import { Arguments, resolveGroupedExpressions } from '../template'
 
 export default class extends Tag {
   value: Value
@@ -24,7 +24,9 @@ export default class extends Tag {
 
         const values: ValueToken[] = []
         while (!token.tokenizer.end()) {
-          values.push(token.tokenizer.readValueOrThrow())
+          const val = token.tokenizer.readValueOrThrow()
+          resolveGroupedExpressions(val, liquid)
+          values.push(val)
           token.tokenizer.skipBlank()
           if (token.tokenizer.peek() === ',') {
             token.tokenizer.readTo(',')

src/tags/for.ts

@@ -2,7 +2,7 @@ import { Hash, ValueToken, Liquid, Tag, evalToken, Emitter, TagToken, TopLevelTo
 import { assertEmpty, isValueToken, toEnumerable } from '../util'
 import { ForloopDrop } from '../drop/forloop-drop'
 import { Parser } from '../parser'
-import { Arguments } from '../template'
+import { Arguments, resolveGroupedExpressions } from '../template'
 
 const MODIFIERS = ['offset', 'limit', 'reversed']
 
@@ -26,6 +26,7 @@ export default class extends Tag {
 
     this.variable = variable.content
     this.collection = collection
+    resolveGroupedExpressions(this.collection, liquid)
     this.hash = new Hash(this.tokenizer, liquid.options.keyValueSeparator)
     this.templates = []
     this.elseTemplates = []

src/template/analysis.ts

@@ -2,6 +2,7 @@ import { Argument, Template, Value } from '.'
 import { isKeyValuePair } from '../parser/filter-arg'
 import { PropertyAccessToken, ValueToken } from '../tokens'
 import {
+  isGroupedExpressionToken,
   isNumberToken,
   isPropertyAccessToken,
   isQuotedToken,
@@ -371,6 +372,16 @@ function * extractValueTokenVariables (token: ValueToken): Generator<Variable> {
   if (isRangeToken(token)) {
     yield * extractValueTokenVariables(token.lhs)
     yield * extractValueTokenVariables(token.rhs)
+  } else if (isGroupedExpressionToken(token)) {
+    for (const t of token.initial.postfix) {
+      if (isValueToken(t)) yield * extractValueTokenVariables(t)
+    }
+    for (const filter of token.filters) {
+      for (const arg of filter.args) {
+        if (isKeyValuePair(arg) && arg[1]) yield * extractValueTokenVariables(arg[1])
+        else if (isValueToken(arg)) yield * extractValueTokenVariables(arg)
+      }
+    }
   } else if (isPropertyAccessToken(token)) {
     yield extractPropertyAccessVariable(token)
   }

src/template/output.ts

@@ -12,7 +12,7 @@ export class Output extends TemplateImpl<OutputToken> implements Template {
   value: Value
   public constructor (token: OutputToken, liquid: Liquid) {
     super(token)
-    const tokenizer = new Tokenizer(token.input, liquid.options.operators, token.file, token.contentRange)
+    const tokenizer = new Tokenizer(token.input, liquid.options.operators, token.file, token.contentRange, liquid.options.groupedExpressions)
     this.value = new Value(tokenizer.readFilteredValue(), liquid)
     const filters = this.value.filters
     const outputEscape = liquid.options.outputEscape

src/template/value.ts

@@ -1,11 +1,29 @@
 import { Filter } from './filter'
 import { Expression } from '../render'
 import { Tokenizer } from '../parser'
-import { assert } from '../util'
-import type { FilteredValueToken } from '../tokens'
+import { assert, isGroupedExpressionToken, isRangeToken, isPropertyAccessToken } from '../util'
+import { FilteredValueToken, Token } from '../tokens'
 import type { Liquid } from '../liquid'
 import type { Context } from '../context'
 
+export function resolveGroupedExpressions (token: Token, liquid: Liquid): void {
+  if (isGroupedExpressionToken(token)) {
+    const fvt = new FilteredValueToken(
+      token.initial, token.filters,
+      token.input, token.begin, token.end, token.file
+    )
+    token.resolvedValue = new Value(fvt, liquid)
+  }
+  if (isRangeToken(token)) {
+    resolveGroupedExpressions(token.lhs, liquid)
+    resolveGroupedExpressions(token.rhs, liquid)
+  }
+  if (isPropertyAccessToken(token)) {
+    if (token.variable) resolveGroupedExpressions(token.variable, liquid)
+    for (const prop of token.props) resolveGroupedExpressions(prop, liquid)
+  }
+}
+
 export class Value {
   public readonly filters: Filter[] = []
   public readonly initial: Expression
@@ -15,10 +33,13 @@ export class Value {
    */
   public constructor (input: string | FilteredValueToken, liquid: Liquid) {
     const token: FilteredValueToken = typeof input === 'string'
-      ? new Tokenizer(input, liquid.options.operators).readFilteredValue()
+      ? new Tokenizer(input, liquid.options.operators, undefined, undefined, liquid.options.groupedExpressions).readFilteredValue()
       : input
     this.initial = token.initial
     this.filters = token.filters.map(token => new Filter(token, this.getFilter(liquid, token.name), liquid))
+    for (const t of this.initial.postfix) {
+      resolveGroupedExpressions(t, liquid)
+    }
   }
 
   public * value (ctx: Context, lenient?: boolean): Generator<unknown, unknown, unknown> {

src/tokens/grouped-expression-token.ts

@@ -0,0 +1,18 @@
+import { Token } from './token'
+import { FilterToken } from './filter-token'
+import { TokenKind } from '../parser'
+import { Expression } from '../render'
+
+export class GroupedExpressionToken extends Token {
+  public resolvedValue?: { value (ctx: any, lenient?: boolean): Generator<unknown, unknown, unknown> }
+  constructor (
+    public initial: Expression,
+    public filters: FilterToken[],
+    public input: string,
+    public begin: number,
+    public end: number,
+    public file?: string
+  ) {
+    super(TokenKind.GroupedExpression, input, begin, end, file)
+  }
+}

src/tokens/index.ts

@@ -16,3 +16,4 @@ export * from './value-token'
 export * from './liquid-tag-token'
 export * from './delimited-token'
 export * from './filtered-value-token'
+export * from './grouped-expression-token'

src/tokens/liquid-tag-token.ts

@@ -16,7 +16,7 @@ export class LiquidTagToken extends DelimitedToken {
     file?: string
   ) {
     super(TokenKind.Tag, [begin, end], input, begin, end, false, false, file)
-    this.tokenizer = new Tokenizer(input, options.operators, file, this.contentRange)
+    this.tokenizer = new Tokenizer(input, options.operators, file, this.contentRange, options.groupedExpressions)
     this.name = this.tokenizer.readTagName()
     this.tokenizer.assert(this.name, 'illegal liquid tag syntax')
     this.tokenizer.skipBlank()