Deep merge meta objects

[okaybroda]

Change meta merge from Object.assign to lodash merge to allow deep merge of meta objects

Closes #1884

[FoxxMD]

I'd like to request a second, optional param added to child() so a customizer function can be applied. I want merge deep functionality but also want arrays to be merged...named values (including arrays) are still overwritten by merge but can be addressed by using mergeWith and a customizer function:

  child(defaultRequestMetadata, customizer = undefined) {
    const logger = this;
    return Object.create(logger, {
      write: {
        value: function (info) {
          const infoClone = mergeWith(
            {},
            defaultRequestMetadata,
            info,
            customizer
          );

          // Object.assign doesn't copy inherited Error
          // properties so we have to do that explicitly
          //
          // Remark (indexzero): we should remove this
          // since the errors format will handle this case.
          //
          if (info instanceof Error) {
            infoClone.stack = info.stack;
            infoClone.message = info.message;
          }

          logger.write(infoClone);
        }
      }
    });
  }

[vincentjames501]

+1

[JaneJeon]

This sounds like a no-brainer. Does any maintainer have any bandwidth for this?

[FoxxMD]

@JaneJeon I ended up forking and implementing my example if you want to use it https://github.com/FoxxMD/winston/tree/feature/deep-merge-meta-object

[maverick1872]

I'd like to request a second, optional param added to child() so a customizer function can be applied. I want merge deep functionality but also want arrays to be merged...named values (including arrays) are still overwritten by merge but can be addressed by using mergeWith and a customizer function:

  child(defaultRequestMetadata, customizer = undefined) {
    const logger = this;
    return Object.create(logger, {
      write: {
        value: function (info) {
          const infoClone = mergeWith(
            {},
            defaultRequestMetadata,
            info,
            customizer
          );

          // Object.assign doesn't copy inherited Error
          // properties so we have to do that explicitly
          //
          // Remark (indexzero): we should remove this
          // since the errors format will handle this case.
          //
          if (info instanceof Error) {
            infoClone.stack = info.stack;
            infoClone.message = info.message;
          }

          logger.write(infoClone);
        }
      }
    });
  }

@FoxxMD Would you be willing to create a Feature Request for this? It's related but we shouldn't be introducing new functionality in a Bugfix PR.

[FoxxMD]

@maverick1872 absolutely. Should I wait until #1989 is merged/finalized before opening a PR?

[maverick1872]

Since they're unrelated no need to wait. Although I will ask if you can give me a day or two prior to creating it. I'm working on introducing some changes to our issue/feature templates to hopefully help with some housekeeping moving forward.

[maverick1872]

@FoxxMD Issue templates updated - feel free to create feature request whenever.

[maverick1872]

Tested your implementation against the new test cases I've developed in #1989. 10 of them are failing so I think it best to close this PR for an alternative implementation. Additionally I'm not a huge fan of introducing new dependencies unless absolutely required.