tor-browser

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layout: page title: Adding a concept-base component permalink: /rfc/0003-concept-base-component

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• Start date: 2020-07-20
• RFC PR: #7776

Summary

Adding a concept-base component for basic interfaces needed by multiple components.

Motivation

We already have a support-base component that contains basic building blocks, like a logger, that other components may need. Some of those building blocks are interfaces, like CrashReporting that are implemented by other components (e.g. lib-crash). This works well in most cases, but becomes problematic once a concept component requires such an interface. Having a concept component depend on actual code with support-base is breaking our contract of concepts only depending on other concepts.

• In #7689 I want to introduce a Profiler interface that allows other components to add profiler markers. The Firefox profiler provides this functionality in our browser-engine-gecko* components (exposed by concept-engine). If this interface lives in support-base then concept-engine would need to depend on support-base.
• In #7775 I want to introduce an interface that allows components to make leaks detectable.

Reference-level explanation

We introduce a concept-base component that contains those "basic" interfaces. Other components and concepts can depend on this component. This component will be the home for the Profiler interface (#7689) and leak detection interface (#7775).

In addition to that we can move interface-only pieces from support-base to concept-base: CrashReporting, MemoryConsumer.

Drawbacks

• This introduces another base component that most other components will depend on. Since it only contains interfaces the impact of that will be low though.

Rationale and alternatives

• Alternatively we could create distinct concept components for every interface theme. This would end up with a very fine-grained list of components that mostly may contain only a single interface. This would also break with the idea that a concept describes a component that will have an actual implementation component (e.g. concept-toolbar -> browser-toolbar). Interfaces like MemoryConsumer are not describing a full component, but instead just one unified aspect of it.