Duplicate "use strict" prologue in the generated output.  #25550

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1. Mohamed Hegazy (mhegazy)

   added

   BugA bug in TypeScriptA bug in TypeScript

   on Jul 10, 2018
2. Mohamed Hegazy (mhegazy)

   added this to the TypeScript 3.0.1 milestone on Jul 10, 2018
3. Mohamed Hegazy (mhegazy)

   assigned

   Wesley Wigham (weswigham)

   on Jul 10, 2018
4. a-tarasyuk commented on Jul 12, 2018

   

   Oleksandr Tarasiuk (a-tarasyuk)

   on Jul 12, 2018

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   Mohamed Hegazy (@mhegazy) Wesley Wigham (@weswigham)

   TS transformer uses node.prepends, which includes build/local/compiler.js (createInputFiles, node.javascriptText). compiler.js has own "use strict" definition - it is the first "use strict"

   The second "use strict" TS transformer adds in the method visitSourceFile because the following condition does not check "use strict" definition in the node.prepends

   const alwaysStrict = getStrictOptionValue(compilerOptions, "alwaysStrict") &&
      !(isExternalModule(node) && moduleKind >= ModuleKind.ES2015) &&
      !isJsonSourceFile(node);

   as the result, tsc.js contains "use strict";"use strict";

   Does that make sense? What do you think?
5. weswigham commented on Jul 12, 2018

   

   Wesley Wigham (weswigham)

   on Jul 12, 2018

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   Yep, that's exactly the problem. To fix it, we need to instantiate a scanner and scan the first of the prepends to see if it already has a use strict statement.
6. weswigham commented on Jul 12, 2018

   

   Wesley Wigham (weswigham)

   on Jul 12, 2018

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   Actually, we should scan all of them and remove any prologues we find and unify them/move them to the top. That has interesting implications for souremapping, too.
7. a-tarasyuk commented on Jul 13, 2018

   

   Oleksandr Tarasiuk (a-tarasyuk)

   on Jul 13, 2018

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   Wesley Wigham (@weswigham) thanks.

   Actually, we should scan all of them and remove any prologues we find and unify them/move them to the top. That has interesting implications for souremapping, too.

   Should we remove prologues from prepends or check if prologues exist in some of them and skip adding "use strict" later? Why I ask, because "compiler.js" has "use strict", and in my opinion, it is right, because "compiler.js" independent file and it should contain "use strict"., just need to skip adding addition prologues later
8. weswigham commented on Jul 17, 2018

   

   Wesley Wigham (weswigham)

   on Jul 17, 2018

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   Oleksandr Tarasiuk (@a-tarasyuk) Keeping them in the intermediate outputs is fine (heck, we should probably even error if they don't all have the same set of prologues - concating a loose file to a strict one could be bad!) - we just need to remove them when concatenating and fixup the resulting concatenated sourcemaps.
9. a-tarasyuk commented on Jul 17, 2018

   

   Oleksandr Tarasiuk (a-tarasyuk)

   on Jul 17, 2018

   Last edited by a-tarasyuk

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   Wesley Wigham (@weswigham) thanks. For instance, during concatenation, we need to remove "use strict" prologue directly in javascriptText(string representation). is it true? I just want to fix and make PR, if you don't mind. :)
10. weswigham commented on Jul 17, 2018

    

    Wesley Wigham (weswigham)

    on Jul 17, 2018

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    I don't think we can remove it on load - since we need to track what we remove to update the sourcemap positions - it should probably just be elided during concatenation itself.
11. a-tarasyuk commented on Jul 18, 2018

    

    Oleksandr Tarasiuk (a-tarasyuk)

    on Jul 18, 2018

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    Wesley Wigham (@weswigham) I thought that we could track "use strict"; prologue when the compiler builds prepends - getPrependNodes, however, it is not true.
12. weswigham commented on Jul 18, 2018

    

    Wesley Wigham (weswigham)

    on Jul 18, 2018

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    Yeah. Instead you wanna create a scanner and scan the text and check the type of the first token.
13. Mohamed Hegazy (mhegazy)

    modified the milestones: TypeScript 3.0.1, TypeScript 3.1 on Jul 18, 2018
14. Ryan Cavanaugh (RyanCavanaugh)

    modified the milestones: TypeScript 3.1, TypeScript 3.2 on Aug 23, 2018
15. DanielRosenwasser commented on Oct 30, 2018

    

    Daniel Rosenwasser (DanielRosenwasser)

    on Oct 30, 2018

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    Oleksandr Tarasiuk (@a-tarasyuk) are you interested in sending a PR for this?
16. Daniel Rosenwasser (DanielRosenwasser)

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    Wesley Wigham (weswigham)

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19. Daniel Rosenwasser (DanielRosenwasser)

    modified the milestones: TypeScript 3.2, TypeScript 3.3 on Nov 8, 2018
20. Sheetal Nandi (sheetalkamat)

    modified the milestones: TypeScript 3.3, TypeScript 3.4.0 on Jan 16, 2019
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22. Sheetal Nandi (sheetalkamat)

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