facebookarchive/prepack

realm.$TemplateMap is persistent throughout effects

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#2129 opened on Jun 18, 2018

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abstractbughelp wantedinterpreterlevel 2 (easy)

Description

Using ES2015 tagged template literals makes use of a $TemplateMap on the realm. When we evaluateForEffects and create a tagged template inside some effects, then revert the effects, it's expected that the newly created array objects in the template map are also stored on effects and properly reverted.

Contributor guide

Tech stack
javascript
Domain
build systemperformance
Issue type
bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
4
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-2 days
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
mostly clear
Prerequisites
Understanding of JavaScript template literalsFamiliarity with prepack's effect system
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
20
Research direction
The issue is about tagged template literals and the `$TemplateMap` on the realm. Investigate the effect system in prepack, specifically how effects are created and reverted when evaluating tagged templates. Look at the relevant source files in the repository, likely in the effects or realm modules, to understand how `$TemplateMap` entries are managed. There are no comments or linked PRs, so the fix requires a thorough understanding of the codebase.