Unexpected results for `detectSubjectType` and `conditionsMatcher` with `PureAbility`

Describe the bug Using a very simply condition to match a class property doesn’t seem to work

To Reproduce Run this code:

import { mongoQueryMatcher, PureAbility, SubjectType } from "@casl/ability";

class Thing {
  static readonly modelName = "Thing";

  public id: string;
}

const ability = new PureAbility(
  [
    {
      action: "read",
      subject: "Thing",
      conditions: [{ id: "abc" }]
    }
  ],
  {
    conditionsMatcher: mongoQueryMatcher,
    detectSubjectType: (subject) => {
      console.log("getting subject for", subject);
      return "Thing" as SubjectType;
    }
  }
);

const thingInstance = new Thing();
thingInstance.id = "abc";

const output = [
  "<br/><b>Thing:</b>",
  `can read Thing (class): ${ability.can("read", Thing)}`,
  `can read Thing (instance): ${ability.can("read", thingInstance)}`,
  `can read Thing (string): ${ability.can("read", "Thing")}`
];

document.body.innerHTML = output.join("<br/>");

The output is:

Thing:
can read Thing (class): false
can read Thing (instance): false
can read Thing (string): true

This is very surprising. I’m providing detectSubjectType and it’s hardcoded to return "Thing" no matter what you pass in. I’m also providing the conditionsMatcher (the default mongo one), and my condition is very simple: The id should match "abc". Why do the first two checks return false?

Expected behavior I would expect the output to be

Thing:
can read Thing (class): true
can read Thing (instance): true
can read Thing (string): true

Interactive example (optional, but highly desirable) https://codesandbox.io/s/casl-example-conditions-and-detectsubjecttype-xp102?file=/src/index.ts

CASL Version

@casl/ability - v5.2.2

Environment: Node v14.15.4 TS 3.9.5

[stalniy]

Indeed, this is missed. I’ll extend docs for detectSubjectType with explanation I gave in this issue.

Thanks 😃

[stalniy]

Well, conditions should be an object and not an array.

update PureAbility doesn’t restrict what you can pass as conditions as this is an extension point and if you pass smth in conditions you need to make sure that conditionsMatcher can correctly process it