What problem does this feature solve?

According to the documentation:

Rsbuild also supports reading .env.[mode] and .env.[mode].local files. You can specify the env mode using the --env-mode flag.

For example, set the env mode as test:

npx rsbuild dev --env-mode test

Rsbuild will then read the following files in sequence:

.env
.env.local
.env.test
.env.test.local

Wouldn't it make sense to read it in reverse? The .env.test.local file has a more specific use-case than .env by definition, so wouldn't one want it to be read first? I am indeed facing this same use-case where I want a .env.<mode>.local file read in precedence to the .env file, which is only used as a template for other .env files.

What does the proposed API look like?

Rsbuild should read the following files in sequence (more specific files should be given precedence):

.env.test.local
.env.test
.env.local
.env

OR

The developer can simply specify the exact .env file they want read.