[WIP] optional dependencies case

[popomore]

Checklist

• [ ] npm test passes
• [ ] tests and/or benchmarks are included
• [ ] documentation is changed or added
• [ ] commit message follows commit guidelines

Affected core subsystem(s)

Description of change

[popomore]

@gxcsoccer 添加一个用例

[codecov[bot]]

Codecov Report

Merging #105 into master will decrease coverage by 60.89%. The diff coverage is n/a.

@@            Coverage Diff            @@
##           master    #105      +/-   ##
=========================================
- Coverage     100%   39.1%   -60.9%     
=========================================
  Files          18      17       -1     
  Lines         958     849     -109     
=========================================
- Hits          958     332     -626     
- Misses          0     517     +517

Impacted Files	Coverage Δ
lib/loader/mixin/controller.js	7.27% <0%> (-92.73%)	:arrow_down:
lib/utils/router.js	10.22% <0%> (-89.78%)	:arrow_down:
lib/loader/mixin/extend.js	12.76% <0%> (-87.24%)	:arrow_down:
lib/loader/context_loader.js	13.63% <0%> (-86.37%)	:arrow_down:
lib/loader/file_loader.js	15.05% <0%> (-84.95%)	:arrow_down:
lib/loader/mixin/config.js	15.38% <0%> (-84.62%)	:arrow_down:
lib/loader/mixin/middleware.js	16.66% <0%> (-83.34%)	:arrow_down:
lib/utils/base_context_class.js	20% <0%> (-80%)	:arrow_down:
lib/utils/index.js	26.66% <0%> (-73.34%)	:arrow_down:
lib/loader/mixin/custom.js	33.33% <0%> (-66.67%)	:arrow_down:
... and 8 more

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[popomore]

这个问题不太好改，现在 hold 吧。