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Scopes of const/let in 2v13.122 #2215

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halemmerich opened this issue May 31, 2022 · 6 comments
Closed

Scopes of const/let in 2v13.122 #2215

halemmerich opened this issue May 31, 2022 · 6 comments

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@halemmerich
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The weather widget exhibits an
weather.wid.js ReferenceError: ReferenceError: "storage" is not defined error with this firmware version. Changing the globally scoped storage var in the lib.js from const to var fixes this. To get the widget to working without errors, there also needs to be a change from let to var for the expiryTimeout variable.

It seems the access from functions to globally defined const/var variables does not yet work correctly.
@halemmerich
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Further experiments show additional variables need changes for full functionality (including Gadgetbridge message parsing).
In lib.js there are const variables B2 and _GB that need to be changed to var.

This is just a workaround, I assume correct solution would be fixing the scope handling.

@gfwilliams
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It seems the access from functions to globally defined const/var variables does not yet work correctly.

Do you think you could give me some short example code of what's not working that should be?

@gfwilliams
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This is very likely related to #2207 and http://forum.espruino.com/conversations/376541/

@halemmerich
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halemmerich commented Jun 6, 2022 •
edited

I have done some experiments and found a relatively small example which seems to show this problem:

Upload this as issue2215:

function test(p){
  console.log("Test", p);
}

let variable_let = { test: test };
const variable_const = { test: test };
var variable_var = { test: test };

exports.func_let = function (){
  variable_let.test("let");
};

exports.func_const = function (){
  variable_const.test("const");
};

exports.func_var = function (){
  variable_var.test("var");
};

The following snippets can then be run from RAM:
Working as expected:

require("issue2215").func_var();
require("issue2215").func_const();
require("issue2215").func_let();

()=>{
  var test = require("issue2215");
  test.func_var();
  test.func_let();
  test.func_const();
}();

Only func_var() working:

()=>{
  let test = require("issue2215");
  test.func_var();
  test.func_let();
  test.func_const();
}();

()=>{
  const test = require("issue2215");
  test.func_var();
  test.func_let();
  test.func_const();
}();

The following is strange to me, this also works:

require("issue2215");
()=>{
  const test = require("issue2215");
  test.func_var();
  test.func_let();
  test.func_const();
}();

@halemmerich
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Adding the example as cached module does not reproduce the problem:

Modules.addCached("issue2215", function() {
  function test(p){
    console.log("Test", p);
  }

  let variable_let = { test: test };
  const variable_const = { test: test };
  var variable_var = { test: test };

  exports.func_let = function (){
    variable_let.test("let");
  };

  exports.func_const = function (){
    variable_const.test("const");
  };

  exports.func_var = function (){
    variable_var.test("var");
  };
});


()=>{
  const test = require("issue2215");
  test.func_var();
  test.func_let();
  test.func_const();
}();

@gfwilliams
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Thanks - well this is all pretty strange!

More stuff...

This breaks:

()=>{
  const x = 5;  
  var test = require("issue2215");
  test.func_var();
  test.func_let();
  test.func_const();
}();

And it'd seem that addCached is effectively like requiring the module first, which is why it fails. Add a const in there and it can fail too:

()=>{
  const x = 5;
  
  Modules.addCached("issue2215", function() {
    function test(p){
      console.log("Test", p);
    }

    let variable_let = { test: test };
    const variable_const = { test: test };
    var variable_var = { test: test };

    exports.func_let = function (){
      variable_let.test("let");
    };

    exports.func_const = function (){
      variable_const.test("const");
    };

    exports.func_var = function (){
      variable_var.test("var");
    };
  });

  var test = require("issue2215");
  test.func_var();
  test.func_let();
  test.func_const();
}();

The issue seems to be that in those cases the const/let are being created in the wrong scope (probably the same one as the first const) - but now I have a self-contained test I should be able to fix it pretty quick - thanks for the help!

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@gfwilliams @halemmerich