Proposal: Unified logging

[daserge]

Cordova unified logging

Note: The issue is associated with Cordova-lib refactoring proposal .

Existing architecture issues and proposed solutions

1. cordova-lib and cordova platforms have logging set up inconsistently

Current implementation details:

• cordova-lib uses EventEmitter, which is further listened in cordova-cli and redirected to console calls,
• Cordova platforms use console methods directly.

This leads to the following issue: log level of cordova-cli doesn't affect platforms at all.

Proposed solutions:
Variant A: Platforms can use EventEmitter passed as a dependency module via PlatformApi' interface (f.e. as a ctor parameter).
In case of CLI-mode cordova-lib EventEmitter will be used (and logs handling will be unified therefore).
In case of platform-standalone mode EventEmitter will be defaulted in the platform.
Variant B: Pass logger class from cordova-lib down to platforms and call its methods further.

Variant A is recommended as it separates aspects of events emitting from logging and is more flexible in terms of substituting logger module.

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2. The log messages aren't standardized

Proposed solution:

• logger module verbosity-based prefixing can be used (WARN :, ERROR:, etc.),
• Emit objects rather than just messages in case of errors (f.e. use CordovaError extended with an error code).

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3. Platforms logging mechanism does not allow plugging in a custom handling code/module (integration & custom transport levels)

Proposed solution:

• Top-level cordova.on event can be used to subscribe for error events since cordova-lib' EventEmitter will be used,
• Additionally logger module used in CLI or platform-standalone mode can be substituted to a pluggable one, for example winston,
• Some multi-transport logger module can be used to use transports other than console (file, couchdb, etc.).

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4. Errors from third-party components (ant, gradle, etc.) can't be easily distinguished

Proposed solution: Attach to process.spawn stdout and stderr, supply caught errors with their source in meta object (f.e. extended CordovaError - see 2.).

[stevengill]

Great writeup! I've been wanting to look at our logging support and standardizing it across our projects.

I like variant A and the idea that can try out different loggers.

I also like the idea of having error codes we define/standardize and use for cordova that persist among our various projects.

[muratsu]

:+1: I'm all in for a standardized logging. Error verbosity will also give us the ability to debug things much more efficiently. This will make verbose mode much more useful.

[nikhilkh]

This is great! I like variant A.

[purplecabbage]

+1 Variant A

[nikhilkh]

Looks like most of this is implemented now. We should close this issue.