Parameter aliases conflict with system query options

lib/csdl2openapi.js

@@ -38,6 +38,23 @@ const TITLE_SUFFIX = {
   "-update": " (for update)",
 };
 
+const SYSTEM_QUERY_OPTIONS = [
+  "compute",
+  "expand",
+  "select",
+  "filter",
+  "search",
+  "count",
+  "orderby",
+  "skip",
+  "top",
+  "format",
+  "index",
+  "schemaversion",
+  "skiptoken",
+  "apply",
+];
+
 /**
  * Construct an OpenAPI description from a CSDL document
  * @param {object} csdl CSDL document
@@ -610,8 +627,8 @@ module.exports.csdl2openapi = function (
             (byKey
               ? "entity from "
               : element.$Collection
-              ? "entities from "
-              : "") +
+                ? "entities from "
+                : "") +
             (level > 0 ? "related " : "") +
             name +
             (byKey ? " by key" : ""),
@@ -1714,7 +1731,13 @@ module.exports.csdl2openapi = function (
         type?.$UnderlyingType == "Edm.Stream"
       ) {
         param.in = "query";
-        if (implicitAliases) {
+        if (
+          implicitAliases &&
+          csdl.$Version !== "2.0" &&
+          SYSTEM_QUERY_OPTIONS.includes(p.$Name.toLowerCase())
+        ) {
+          param.name = "@" + p.$Name;
+        } else if (implicitAliases) {
           param.name = p.$Name;
         } else {
           pathSegments.push(p.$Name + "=@" + p.$Name);
@@ -1740,7 +1763,13 @@ module.exports.csdl2openapi = function (
           pathSegments.push(p.$Name + "={" + p.$Name + "}");
           param.in = "path";
         }
-        param.name = p.$Name;
+        if (
+          implicitAliases &&
+          csdl.$Version !== "2.0" &&
+          SYSTEM_QUERY_OPTIONS.includes(p.$Name.toLowerCase())
+        )
+          param.name = "@" + p.$Name;
+        else param.name = p.$Name;
         if (
           !p.$Type ||
           p.$Type === "Edm.String" ||

test/csdl2openapi.test.js

@@ -929,6 +929,75 @@ describe("Edge cases", function () {
     );
   });
 
+  it("function with @ parameter aliases", function () {
+    const csdl = {
+      $Version: "4.01",
+      $Reference: {
+        dummy: {
+          $Include: [{ $Namespace: "Org.OData.Core.V1", $Alias: "Core" }],
+        },
+      },
+      $EntityContainer: "model.Container",
+      model: {
+        $Alias: "this",
+        FavoritePhotos: [
+          {
+            $Kind: "Function",
+            $Parameter: [
+              {
+                $Name: "SKIP",
+                $Type: "Edm.Date",
+                $Collection: true,
+                "@Core.Description": "Dates to be skipped",
+              },
+              {
+                $Name: "filter",
+                "@Core.Description": "Boolean expression to filter the result",
+              },
+            ],
+            $ReturnType: {},
+          },
+        ],
+        Container: {
+          fav: { $Function: "this.FavoritePhotos" },
+        },
+      },
+    };
+    const expected = {
+      paths: {
+        "/fav": {
+          get: {
+            parameters: [
+              {
+                name: "@SKIP",
+                in: "query",
+                required: true,
+                description:
+                  "Dates to be skipped  \nThis is a URL-encoded JSON array with items of type Edm.Date, see [Complex and Collection Literals](https://docs.oasis-open.org/odata/odata/v4.01/odata-v4.01-part2-url-conventions.html#sec_ComplexandCollectionLiterals)",
+                schema: { type: "string" },
+                example: "[]",
+              },
+              {
+                name: "@filter",
+                in: "query",
+                required: true,
+                schema: { type: "string", pattern: "^'([^']|'')*'$" },
+                description:
+                  "Boolean expression to filter the result  \nString value needs to be enclosed in single quotes",
+              },
+            ],
+            summary: "Invoke function FavoritePhotos",
+            tags: ["Service Operations"],
+          },
+        },
+      },
+    };
+    const actual = csdl2openapi(csdl, { diagram: true });
+    delete actual.paths["/$batch"];
+    delete actual.paths["/fav"].get.responses;
+    assert.deepStrictEqual(actual.paths, expected.paths);
+  });
+
   it("return type with facets", function () {
     const csdl = {
       $EntityContainer: "this.Container",