feat(core): optimize default value handling for options.locales

[pengzhanbo]

Before submitting the PR, please make sure you do the following

• Read the Contributing Guidelines.
• Provide a description in this PR that addresses what the PR is solving. If this PR is going to solve an existing issue, please reference the issue (e.g. close #123).

What is the purpose of this pull request?

• Bug fix
• New feature
• Documentation update
• Other

Description

Screenshots

Before

After

[coveralls]

Pull Request Test Coverage Report for Build 21939083597

Details

• 2 of 2 (100.0%) changed or added relevant lines in 1 file are covered.
• 1 unchanged line in 1 file lost coverage.
• Overall coverage decreased (-0.05%) to 73.993%

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Files with Coverage Reduction	New Missed Lines	%
packages/shared/src/utils/routes/resolveLocalePath.ts	1	92.86%

Totals
Change from base Build 21831331239:	-0.05%
Covered Lines:	700
Relevant Lines:	946

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💛 - Coveralls

[Mister-Hope]

I think this is not what I mean.

In short, a / and /404.html shall exist. These belong to locale /, then locale / MUST exist.

A plugin can also choose to generate a /plugin.html.

The or should ensure to generate a locale /

[Mister-Hope]

I think this is not what I mean.

In short, a / and /404.html shall exist. These belong to locale /, then locale / MUST exist.

A plugin can also choose to generate a /plugin.html.

The or should ensure to generate a locale /

[pengzhanbo]

Because the time interval is a bit long, what was the solution we discussed back then?
@Mister-Hope

[Mister-Hope]

Locales object and its / key must exist, with a lang inferred from root lang if absent