Do not (exclusively) rely on class name to execute migration steps (e.g. use decorator instead)

[dominic-simplan]

Issue type:

[ ] question
[ ] bug report
[x] feature request
[ ] documentation issue

Database system/driver:

[ ] cordova
[ ] mongodb
[ ] mssql
[ ] mysql / mariadb
[ ] oracle
[ ] postgres
[x] sqlite
[ ] sqljs
[ ] react-native
[ ] expo

TypeORM version:

[x] latest
[ ] @next
[ ] 0.x.x (or put your version here)

Currently migrations seem to rely on the class name to execute migrations correctly. This causes issues if the mangle option of UglifyJS is enabled, as the class names are mangled. Wouldn't it be possible to use a decorator to define the timestamp instead? E.g:

@Migration(1529582677992)
export class InitialTables implements MigrationInterface {
}

As a workaround I currently pass the migration class names to the reserved option of UglifyJS, which is quite error-prone in the long run:

mangle: {
    reserved: ["InitialTables1529582677992", "AddForeignKeys1529588981853", "AddTable1531748224253"]
}

[pleerock]

I would like to avoid using another decorator. What we can do is to add extra optional properties into MigrationInterface that users can implement and use for custom migration name. Feel free to contribute!

[liangchunn]

I've hit a similar issue with normal relations as well (webpack build).

When EntityMetadataValidator.validateDependencies() is executed in a mangled file, it can happen that there are duplicate identifiers for a particular class as a result of the Function.prototype.name call

  entityMetadatas.forEach(entityMetadata => {
    graph.addNode(entityMetadata.name);
+   console.log(entityMetadata.name)
  });

With keep_fnames: false with terser/uglify,

p
u
d  <--
c
l
y
d  <--
(node:31945) UnhandledPromiseRejectionWarning: 
CircularRelationsError: Circular relations detected: p -> d -> d. 
...

Using keep_fnames: true fixes this and no error is thrown:

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If a webpack build is being managed by another tool (like create-react-app), it might be almost impossible to override terser's/uglifyjs's configuration.