c8 coverage seems broken when using import.meta.env

[Polluux]

Describe the bug

Hi,
I'm using c8 for test coverage in a Vite/Vue project and encountered an issue when using import.meta.env.
Vue project is written in OptionAPI, and .vue files import .ts files.
When using import.meta.env in an imported .ts file, coverage report indicate only 1 line, and 100% coverage.
Commenting the line causes the coverage report to display correct values.
(Running test with istanbul does not raise this issue.)
(Using script in .vue as SFC does not raise this issue.)

Result:
Statements : 100% ( 7/7 )
Branches : 100% ( 0/0 )
Functions : 100% ( 0/0 )
Lines : 100% ( 7/7 )

Expected Result:
Statements : 94.73% ( 18/19 )
Branches : 50% ( 1/2 )
Functions : 100% ( 1/1 )
Lines : 94.73% ( 18/19 )

Reproduction

Here is a repository to reproduce : https://github.com/Polluux/demo-c8-issues
(Note : This repository contains multiple issues for c8)

System Info

System: 
  Ubuntu 22.04.1 LTS x86_64 GNU/Linux
Node:
  v16.15.1
Dependencies:
  "vue": "^3.2.45"
  "@vitejs/plugin-vue": "^4.0.0",
  "@vitest/coverage-c8": "^0.26.0",
  "@vue/test-utils": "2.2.6",
  "c8": "^7.12.0",
  "jsdom": "^20.0.3",
  "typescript": "^4.9.4",
  "vite": "^4.0.2",
  "vitest": "^0.26.0",
  "vue-tsc": "^1.0.14"

Used Package Manager

npm

Validations

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• Read the Contributing Guidelines.
• Read the docs.
• Check that there isn't already an issue that reports the same bug to avoid creating a duplicate.
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• The provided reproduction is a minimal reproducible example of the bug.

[Polluux]

Using process.env instead of import.meta.env does not raise this issue neither.

[AriPerkkio]

I'm able to reproduce the issue and can fix it by modifying the C8 provider's map.sourcesContent. Below on the left side is the fixed case, right one is the original one. @Polluux I guess the left side looks as expected?

Manipulating the map.sourcesContent directly does not seem like right solution though. Need to study the root cause in more details.
This is likely causing some of the other reported C8 issues.