Multiple assets emit different content to the same filename error for assets with persistent cache

首先使用 ng build 和 webpack 5 持久化快取重現問題：在不同資料夾中使用兩個檔名相同的 SVG 資產，然後在不同建置之間變更它們的匯入順序。追蹤已快取資產和新造訪資產的輸出方式。完成標準是，重複建置不再向同一檔名輸出不同內容，也不再引發 webpack 衝突錯誤。

🐞 Bug report

Command (mark with an x)

• new
• build
• serve
• test
• e2e
• generate
• add
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• lint
• extract-i18n
• run
• config
• help
• version
• doc

Is this a regression?

No

Description

This issue is a continuation for the https://github.com/angular/angular-cli/issues/12186. The fix, introduced for that issue, does not correctly work when using webpack 5 persistent cache.

The problem comes from the fact that when you have multiple assets with the same name, but different folder, CLI emits the first visited asset to the root of fs(disregarding it's folder path), while emiting subsequent assets with this name to their corresponding folders.

To do that Angular CLI keeps track of the emitted(visited) files in-memory, and it does not work when part of the compilation was restored from file system cache. This makes it so that CLI does not realise that a certain svg file was previously emited to the root of the fs, which in turn may lead to the emition of a different svg file(with the same name, but different content) to the same place in the root of the fs, triggering webpack emit conflict error.

🔬 Minimal Reproduction

1. Enable webpack 5 persistent cache feature
2. Make sure the cache is clear
3. Create a project with 2 different SVG assets with the same name, but place them in two different folders
4. Import one of this images somewhere in the code of the project
5. Run ng build. The svg is emitted to the root of fs, and is cached
6. Change the code to import second image right before the first one
7. Run ng build again. CLI will try to emit the second svg to the root of fs, but there is already the first svg retrieved from the cache there.
8. You should see the webpack emit conflict error.

🔥 Exception or Error

Error: Conflict: Multiple assets emit different content to the same filename empty.svg

🌍 Your Environment

Angular CLI: 12.2.0
Node: 14.17.3
Package Manager: npm 6.14.13
OS: darwin x64

Angular: 12.2.0
... animations, cdk, cli, common, compiler, compiler-cli, core
... forms, platform-browser, platform-browser-dynamic, router

Package                         Version
---------------------------------------------------------
@angular-devkit/architect       0.1202.0
@angular-devkit/build-angular   12.2.0
@angular-devkit/core            12.2.0
@angular-devkit/schematics      12.2.0
@schematics/angular             12.2.0
rxjs                            6.6.7
typescript                      4.2.4
webpack                         5.47.1