feat: add find_index, has, and reject filters (#799)

* feat: add find_index, has, and reject filters

* Minor tweaks

* Change semantics of jekyllStyle, add more tests

* Some docs improvements

src/filters/array.ts

@@ -117,7 +117,17 @@ export function slice<T> (this: FilterImpl, v: T[] | string, begin: number, leng
   return v.slice(begin, begin + length)
 }
 
-export function * where<T extends object> (this: FilterImpl, arr: T[], property: string, expected?: any): IterableIterator<unknown> {
+function expectedMatcher (this: FilterImpl, expected: any): (v: any) => boolean {
+  if (this.context.opts.jekyllWhere) {
+    return (v: any) => EmptyDrop.is(expected) ? equals(v, expected) : (isArray(v) ? arrayIncludes(v, expected) : equals(v, expected))
+  } else if (expected === undefined) {
+    return (v: any) => isTruthy(v, this.context)
+  } else {
+    return (v: any) => equals(v, expected)
+  }
+}
+
+function * filter<T extends object> (this: FilterImpl, include: boolean, arr: T[], property: string, expected: any): IterableIterator<unknown> {
   const values: unknown[] = []
   arr = toArray(arr)
   this.context.memoryLimit.use(arr.length)
@@ -125,16 +135,11 @@ export function * where<T extends object> (this: FilterImpl, arr: T[], property:
   for (const item of arr) {
     values.push(yield evalToken(token, this.context.spawn(item)))
   }
-  const matcher = this.context.opts.jekyllWhere
-    ? (v: any) => EmptyDrop.is(expected) ? equals(v, expected) : (isArray(v) ? arrayIncludes(v, expected) : equals(v, expected))
-    : (v: any) => equals(v, expected)
-  return arr.filter((_, i) => {
-    if (expected === undefined) return isTruthy(values[i], this.context)
-    return matcher(values[i])
-  })
+  const matcher = expectedMatcher.call(this, expected)
+  return arr.filter((_, i) => matcher(values[i]) === include)
 }
 
-export function * where_exp<T extends object> (this: FilterImpl, arr: T[], itemName: string, exp: string): IterableIterator<unknown> {
+function * filter_exp<T extends object> (this: FilterImpl, include: boolean, arr: T[], itemName: string, exp: string): IterableIterator<unknown> {
   const filtered: unknown[] = []
   const keyTemplate = new Value(stringify(exp), this.liquid)
   const array = toArray(arr)
@@ -143,11 +148,27 @@ export function * where_exp<T extends object> (this: FilterImpl, arr: T[], itemN
     this.context.push({ [itemName]: item })
     const value = yield keyTemplate.value(this.context)
     this.context.pop()
-    if (value) filtered.push(item)
+    if (value === include) filtered.push(item)
   }
   return filtered
 }
 
+export function * where<T extends object> (this: FilterImpl, arr: T[], property: string, expected?: any): IterableIterator<unknown> {
+  return yield * filter.call(this, true, arr, property, expected)
+}
+
+export function * reject<T extends object> (this: FilterImpl, arr: T[], property: string, expected?: any): IterableIterator<unknown> {
+  return yield * filter.call(this, false, arr, property, expected)
+}
+
+export function * where_exp<T extends object> (this: FilterImpl, arr: T[], itemName: string, exp: string): IterableIterator<unknown> {
+  return yield * filter_exp.call(this, true, arr, itemName, exp)
+}
+
+export function * reject_exp<T extends object> (this: FilterImpl, arr: T[], itemName: string, exp: string): IterableIterator<unknown> {
+  return yield * filter_exp.call(this, false, arr, itemName, exp)
+}
+
 export function * group_by<T extends object> (this: FilterImpl, arr: T[], property: string): IterableIterator<unknown> {
   const map = new Map()
   arr = toEnumerable(arr)
@@ -176,26 +197,57 @@ export function * group_by_exp<T extends object> (this: FilterImpl, arr: T[], it
   return [...map.entries()].map(([name, items]) => ({ name, items }))
 }
 
-export function * find<T extends object> (this: FilterImpl, arr: T[], property: string, expected: string): IterableIterator<unknown> {
+function * search<T extends object> (this: FilterImpl, arr: T[], property: string, expected: string): IterableIterator<unknown> {
   const token = new Tokenizer(stringify(property)).readScopeValue()
   const array = toArray(arr)
-  for (const item of array) {
-    const value = yield evalToken(token, this.context.spawn(item))
-    if (equals(value, expected)) return item
+  const matcher = expectedMatcher.call(this, expected)
+  for (let index = 0; index < array.length; index++) {
+    const value = yield evalToken(token, this.context.spawn(array[index]))
+    if (matcher(value)) return [index, array[index]]
   }
 }
 
-export function * find_exp<T extends object> (this: FilterImpl, arr: T[], itemName: string, exp: string): IterableIterator<unknown> {
+function * search_exp<T extends object> (this: FilterImpl, arr: T[], itemName: string, exp: string): IterableIterator<unknown> {
   const predicate = new Value(stringify(exp), this.liquid)
   const array = toArray(arr)
-  for (const item of array) {
-    this.context.push({ [itemName]: item })
+  for (let index = 0; index < array.length; index++) {
+    this.context.push({ [itemName]: array[index] })
     const value = yield predicate.value(this.context)
     this.context.pop()
-    if (value) return item
+    if (value) return [index, array[index]]
   }
 }
 
+export function * has<T extends object> (this: FilterImpl, arr: T[], property: string, expected?: any): IterableIterator<unknown> {
+  const result = yield * search.call(this, arr, property, expected)
+  return !!result
+}
+
+export function * has_exp<T extends object> (this: FilterImpl, arr: T[], itemName: string, exp: string): IterableIterator<unknown> {
+  const result = yield * search_exp.call(this, arr, itemName, exp)
+  return !!result
+}
+
+export function * find_index<T extends object> (this: FilterImpl, arr: T[], property: string, expected?: any): IterableIterator<unknown> {
+  const result = yield * search.call(this, arr, property, expected)
+  return result ? result[0] : undefined
+}
+
+export function * find_index_exp<T extends object> (this: FilterImpl, arr: T[], itemName: string, exp: string): IterableIterator<unknown> {
+  const result = yield * search_exp.call(this, arr, itemName, exp)
+  return result ? result[0] : undefined
+}
+
+export function * find<T extends object> (this: FilterImpl, arr: T[], property: string, expected?: any): IterableIterator<unknown> {
+  const result = yield * search.call(this, arr, property, expected)
+  return result ? result[1] : undefined
+}
+
+export function * find_exp<T extends object> (this: FilterImpl, arr: T[], itemName: string, exp: string): IterableIterator<unknown> {
+  const result = yield * search_exp.call(this, arr, itemName, exp)
+  return result ? result[1] : undefined
+}
+
 export function uniq<T> (this: FilterImpl, arr: T[]): T[] {
   arr = toArray(arr)
   this.context.memoryLimit.use(arr.length)