Split `ConfigConvert` into readers and writers #179

ruippeixotog · 2017-03-21T17:52:23Z

In this PR ConfigConvert is redefined as an union of two new traits: ConfigReader for reading objects from configs and ConfigWriter to write objects to configs.

ConfigConvert continues to exist and I think it still plays an important role in pureconfig. Most of the times users will be able to define both operations for a type, and for organization purposes it's good to define them together. However, with PR users will be able to define only one of the operations and still use operations such as loadConfig and toConfig, which is particularly useful for some particular models that only have a one-way conversion.

I opted to split the BasicConverters and DerivedConverters in readers and writers in order to mix into the companion objects of ConfigReader and ConfigWriter only the implicits that mattered to each one. However, it definitely doesn't have to be the case and I think we should leave the ConfigConvert definitions in pureconfig modules as they are. A ConfigConvert can be seen both as a ConfigReader as a ConfigWriter`, and in the modules we don't have any advantage in splitting them.

This change, when seen together with #171, is source-compatible with the latest version 0.6.0. If we do a release without this PR it may be possible for users to start using BasicConverters and DerivedConverters directly and this PR causes them to disappear.

Closes #92.

ruippeixotog · 2017-03-21T17:52:37Z

This PR is a WIP as it is still missing tests and documentation. I'd like to get some feedback from you before starting writing documentation. I'll be writing tests meanwhile.

coveralls · 2017-03-21T18:26:57Z

Coverage increased (+2.1%) to 73.375% when pulling 86d5331 on ruippeixotog:split-readers-and-writers into 721603b on melrief:master.

coveralls · 2017-03-21T22:10:53Z

Coverage increased (+2.1%) to 73.375% when pulling 86cc9c1 on ruippeixotog:split-readers-and-writers into 721603b on melrief:master.

coveralls · 2017-03-21T22:10:53Z

Coverage increased (+2.1%) to 73.375% when pulling 86cc9c1 on ruippeixotog:split-readers-and-writers into 721603b on melrief:master.

coveralls · 2017-03-21T22:15:08Z

Coverage increased (+2.1%) to 73.375% when pulling 86cc9c1 on ruippeixotog:split-readers-and-writers into 721603b on melrief:master.

melrief

I'm not sure why this is still WIP, I've read the PR and I think it's nice. I have no comments.

ruippeixotog · 2017-03-22T14:33:11Z

This PR is a WIP as it is still missing tests and documentation. However, as the tests for ConfigConvert still check both parts of the conversion, I don't think anything more is necessary for now. If you agree with the PR as it is now, I'll update the README and then we can merge this.

melrief · 2017-03-22T20:54:29Z

@ruippeixotog I'm concerned about possible conflicts with #178 , do you think we should wait for that to be merged before we change the documentation?

ruippeixotog · 2017-03-22T21:20:22Z

Good question... I guess it's better if this is merged without the documentation then and I'll do another PR later, after #178. That way no one will have much trouble dealing with merge conflicts.

melrief · 2017-03-22T21:27:58Z

Agreed, I'll wait for another approve and then merge

melrief · 2017-03-23T18:49:14Z

core/src/main/scala/pureconfig/ConvertHelpers.scala

@@ -94,36 +102,68 @@ trait ConvertHelpers {
    override def to(t: T): ConfigValue = ConfigValueFactory.fromAnyRef(t)
  }

-  def fromStringReader[T](fromF: String => Option[ConfigValueLocation] => Either[ConfigReaderFailure, T]): ConfigConvert[T] = new ConfigConvert[T] {
+  def fromStringReader[T](fromF: String => Option[ConfigValueLocation] => Either[ConfigReaderFailure, T]): ConfigReader[T] = new ConfigReader[T] {


Do you think we should move reader/writer helpers in the Reader/Writer companion object? I think it could be nice to have ConfigReader.fromString instead of ConverterHelper.fromStringReader. You don't need the Reader at the end of fromStringReader if the object in which the method is defined is a Reader (I hope I explained myself). What do you think?

Yes, that's a good idea! I'll move all the methods, but I'll leave forwarder deprecated methods in ConfigConvert in order not to break compatibility here, ok?

ruippeixotog · 2017-03-24T00:36:12Z

@melrief besides the renaming you suggested, I ended up doing a greater number of changes in order to keep the code clean and with consistent names in 3a9823b.

ConvertHelpers doesn't have factory methods anymore, not even ConfigConvert ones. It ended up with nothing more than... helpers. All factory methods were moved to the adequate companion object. I prefer to have all constructors directly in the companion object and not in a separate trait, and I also like that the companion objects are not polluted anymore with methods not relating to them directly.

I tried to match the factory method name to the type of entity to build. ConfigReader has the fromString factory method family, with all try/option and non-empty variants. ConfigWriter has forPrimitive, toDefaultString and toString factory methods. ConfigConvert has a viaString factory method family like ConfigReader.

I left a large number of deprecated constructors in ConfigConvert in order not to break existing code. I hope I didn't forget any method, but everything should be there.

Let me know what you think of it now!

coveralls · 2017-03-24T00:58:54Z

Coverage decreased (-0.8%) to 71.37% when pulling 14f15fc on ruippeixotog:split-readers-and-writers into 0528096 on melrief:master.

I have to have a look at the last changes

melrief · 2017-03-24T09:27:20Z

@ruippeixotog thanks for the changes, the new API is much nicer in my opinion! I don't have time to do the review but tomorrow I'll have a look in deep.

melrief

Nice, I like the new API for ConfigReader and ConfigWriter even more. I'm waiting for another review.

leifwickland · 2017-03-28T04:49:30Z

core/src/main/scala/pureconfig/ConfigConvert.scala

-}
+trait ConfigConvert[T] extends ConfigReader[T] with ConfigWriter[T]
+
+object ConfigConvert extends ConvertHelpers {


Suggestion: Add a class-level comment like:

/** * This object provides methods to create [ConfigConvert] instances. */

Added in 5845cac.

leifwickland · 2017-03-28T04:50:01Z

core/src/main/scala/pureconfig/ConfigReader.scala

+  def from(config: ConfigValue): Either[ConfigReaderFailures, T]
+}
+
+object ConfigReader extends BasicReaders with DerivedReaders {


Suggestion: Add a class-level comment like:

/** * This object provides methods to create [ConfigReader] instances. */

Added in 5845cac.

leifwickland · 2017-03-28T04:50:20Z

core/src/main/scala/pureconfig/ConfigWriter.scala

+  def to(t: T): ConfigValue
+}
+
+object ConfigWriter extends BasicWriters with DerivedWriters {


Suggestion: Add a class-level comment like:

/** * This object provides methods to create [ConfigWriter] instances. */

Added in 5845cac.

leifwickland · 2017-03-28T04:54:03Z

core/src/main/scala/pureconfig/DerivedWriters.scala

+    override def to(t: FieldType[K, V] :: T): ConfigValue = {
+      val keyStr = hint.configKey(key.value.toString().tail)
+      val rem = tConfigWriter.value.to(t.tail)
+      // TODO check that all keys are unique


The immortal TODO lives on.

I think we should address old TODOs in another PR because this one is dealing with enough stuff :-)

I agree with @leifwickland. The comment is still relevant and unrelated to this PR.

leifwickland · 2017-03-28T04:55:08Z

core/src/main/scala/pureconfig/DerivedWriters.scala

+
+      override def to(t: FieldType[Name, V] :+: T): ConfigValue = t match {
+        case Inl(l) =>
+          // Writing a coproduct to a config can fail. Is it worth it to make `to` return a `Try`?


Is this the next great zombie comment?

I believe the comment is still relevant - it mentions a question for which there is still no clear answer. Though it may not be the best place to make TODOs and discussion topics visible, I don't mind having comments like this around for as long as it takes.

leifwickland

Kudos, @ruippeixotog! This was a huge change that seems to be have executed extremely well.
I offered a couple suggestions, but this LGTM. 👍

…onvert

ruippeixotog · 2017-03-28T13:32:00Z

I have just fixed the merge conflicts. Unless you want to wait for @jcazevedo to review this, this is ready to merge, @melrief.

@leifwickland I believe I replied to all your comments. Please let me know if you see anything else :)

jcazevedo

This looks good to merge as is! Sorry for not reviewing it earlier.

* Update README with the changes in #179 * Add missing type param in loadConfig

ruippeixotog requested review from jcazevedo, leifwickland, melrief and derekmorr March 21, 2017 17:52

melrief previously approved these changes Mar 22, 2017

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ruippeixotog changed the title ~~[WIP] Split ConfigConvert into readers and writers~~ Split ConfigConvert into readers and writers Mar 22, 2017

melrief reviewed Mar 23, 2017

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melrief approved these changes Mar 24, 2017

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leifwickland reviewed Mar 28, 2017

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leifwickland approved these changes Mar 28, 2017

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derekmorr approved these changes Mar 28, 2017

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ruippeixotog added 2 commits March 28, 2017 14:03

Split ConfigConvert into reader and writer type classes

6fdabba

Relax type requirements of loadConfig-like and toConfig-like methods

f4b40cf

ruippeixotog added 4 commits March 28, 2017 14:03

Remove useless comments

790e0aa

Reorganize factory methods for ConfigReader, ConfigWriter and ConfigC…

98ff950

…onvert

Correct deprecation messages

f954d52

Fix tut examples

0273b1a

Add Scaladoc to companion objects

1b1c6a5

jcazevedo approved these changes Mar 28, 2017

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ruippeixotog merged commit 2278666 into pureconfig:master Mar 28, 2017

ruippeixotog deleted the split-readers-and-writers branch March 28, 2017 20:43

melrief pushed a commit that referenced this pull request Mar 31, 2017

Add entries in the CHANGELOG for #179 (#196)

ca92131

melrief pushed a commit that referenced this pull request Mar 31, 2017

Update README with the changes in #179 (#197)

6e94950

* Update README with the changes in #179 * Add missing type param in loadConfig

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Split `ConfigConvert` into readers and writers #179

Split `ConfigConvert` into readers and writers #179

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Split ConfigConvert into readers and writers #179

Split ConfigConvert into readers and writers #179

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Split `ConfigConvert` into readers and writers #179

Split `ConfigConvert` into readers and writers #179

ruippeixotog commented Mar 24, 2017 •

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