Add optional name to MigrationInterface (fixes #3933)

[leonardofalk]

This fixes a problem when after minification process, migrations cannot be loaded because their name is changed to some random value, this happens mostly when using react-native/expo.

There are several topics about this issue in facebook/metro and typeorm repositories, but I couldn't find any pull request for it. It could be fixed by changing the default minifier, but that can break other stuff.

There are also a few steps before merging this PR:

• If this field sould be called 'migrationName'? Other options could be 'displayName' or simply 'name'.

• Should migrations generated with the CLI contain this attribute by default?

EDIT

Created a babel-plugin to automatically add name property:

module.exports = function({ types: t }, options) {
  return {
    visitor: {
      ClassDeclaration(path) {
        const migrationName = t.stringLiteral(path.node.id.name)
        const migrationTimestamp = parseInt(migrationName.value.substr(-13), 10)

        if (!isNaN(migrationTimestamp)) {
          const prop = t.classProperty(t.identifier(options.property), migrationName, null, null)

          path.node.body.body.push(prop)
        }
      },
    },
  }
}

{
  presets: ['module:metro-react-native-babel-preset'],
  plugins: [
    ['babel-plugin-typeorm-migration-name', { property: 'migrationName' }]
  ],
}

[pleerock]

If this field sould be called 'migrationName'? Other options could be 'displayName' or simply 'name'.

simply name looks fine

Should migrations generated with the CLI contain this attribute by default?

not sure, but we can add it

[leonardofalk]

If this field sould be called 'migrationName'? Other options could be 'displayName' or simply 'name'.

simply name looks fine

Should migrations generated with the CLI contain this attribute by default?

not sure, but we can add it

Done, changed to name and added it to the migration template.