fix($filter): Properly handle truthy values. Closes #320

kofrasa · Mar 28, 2023 · 7c59005 · 7c59005
1 parent 8ba5ea7
commit 7c59005
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Showing 3 changed files with 36 additions and 24 deletions.
diff --git a/src/core.ts b/src/core.ts
@@ -96,7 +96,8 @@ export interface Options {
   /**
    * Enforces strict MongoDB compatibilty. See readme for differences. @default true.
    * When disabled, the following behaviours take effect.
-   *  - $elemMatch projection operator returns all matching nested documents instead of only the first.
+   *  * $elemMatch projection operator returns all matching nested documents instead of only the first.
+   *  * $filter expression treats empty string "" as falsey consistent with Javascript.
    */
   readonly useStrictMode?: boolean;
   /**

diff --git a/src/operators/expression/array/filter.ts b/src/operators/expression/array/filter.ts
@@ -7,9 +7,9 @@ import { assert, isArray } from "../../../util";
 /**
  * Selects a subset of the array to return an array with only the elements that match the filter condition.
  *
- * @param  {Object} obj  [description]
- * @param  {*} expr [description]
- * @return {*}      [description]
+ * @param  {Object} obj The current document
+ * @param  {*} expr The filter spec
+ * @return {*}
  */
 export function $filter(
   obj: RawObject,
@@ -21,15 +21,18 @@ export function $filter(
 
   const copts = ComputeOptions.init(options, obj);
   const k = expr.as || "this";
-  return input.filter(
-    (o: AnyVal) =>
-      computeValue(
-        obj,
-        expr.cond,
-        null,
-        copts.update(copts.root, {
-          variables: { [k]: o },
-        })
-      ) === true
-  );
+  const local = {
+    variables: { [k]: null },
+  };
+  return input.filter((o: AnyVal) => {
+    local.variables[k] = o;
+    const b = computeValue(
+      obj,
+      expr.cond,
+      null,
+      copts.update(copts.root, local)
+    );
+    // allow empty strings only in strict MongoDB mode (default).
+    return !!b || (b === "" && options.useStrictMode);
+  });
 }
diff --git a/test/operators/expression/array/filter.test.ts b/test/operators/expression/array/filter.test.ts
@@ -4,16 +4,24 @@ support.runTest(support.testPath(__filename), {
   $filter: [
     [
       {
-        input: [1, "a", 2, null, 3.1, 4, "5"],
-        as: "num",
-        cond: {
-          $and: [
-            { $gte: ["$$num", Number.MIN_SAFE_INTEGER] },
-            { $lte: ["$$num", Number.MAX_SAFE_INTEGER] },
-          ],
-        },
+        input: [
+          "string",
+          "",
+          1,
+          0,
+          1.5,
+          NaN,
+          undefined,
+          null,
+          true,
+          false,
+          [],
+          {},
+        ],
+        as: "item",
+        cond: "$$item",
       },
-      [1, 2, 3.1, 4],
+      ["string", "", 1, 1.5, true, [], {}],
     ],
   ],
 });