Usage of `ESObject` type is restricted

Rule arkts-limited-esobj

Severity: warning

ArkTS does not allow using ESObject type in some cases. The most part of limitations are put in place in order to prevent spread of dynamic objects in the static codebase. The only scenario where it is permited to use ESObject as type specifier is in local variable declaration. Initialization of variables with ESObject type is also limited. Such variables can only be initialized with values that originate from interop: other ESObject typed variables, any, unknown, variables with anonymous type, etc. It is prohibited to initialize ESObject typed variable with statically typed value. Varaible of type ESObject can only be passed to interop calls and assigned to other variables of type ESObject.

ArkTS

    // lib.d.ts
    declare function foo(): any;
    declare function bar(a: any): number;

    // main.ets
    let e0: ESObject = foo(); // CTE - ``ESObject`` typed variable can only be local

    function f() {
        let e1 = foo(); // CTE - type of e1 is `any`
        let e2: ESObject = 1; // CTE - can't initialize ESObject with not dynamic values
        let e3: ESObject = {}; // CTE - can't initialize ESObject with not dynamic values
        let e4: ESObject = []; // CTE - can't initialize ESObject with not dynamic values
        let e5: ESObject = ""; // CTE - can't initialize ESObject with not dynamic values
        e5['prop'] // CTE - can't access dynamic properties of ESObject
        e5[1] // CTE - can't access dynamic properties of ESObject
        e5.prop // CTE - can't access dynamic properties of ESObject

        let e6: ESObject = foo(); // OK - explicitly annotaded as ESObject
        let e7 = e6; // OK - initialize ESObject with ESObject
        bar(e7) // OK - ESObject is passed to interop call
    }

Usage of ESObject type is restricted

ArkTS

See also

Usage of `ESObject` type is restricted