`Collectors.toMap` handling for streams #938

msridhar · 2024-03-22T22:47:05Z

Fixes #934

The key new thing with the support here is we have further nesting. Rather than a map method, where the relevant lambda is passed directly:

stream.filter(foo -> foo.bar != null).map(foo -> foo.bar.baz)

In this case we have a collect call, which gets as its argument the result of Collectors.toMap, and the relevant lambdas are passed to toMap:

stream
  .filter(foo -> foo.bar != null)
  .collect(Collectors.toMap(foo -> foo.bar.baz, foo -> foo.bar.other))

Supporting this requires some new types of logic in our streams handler (particularly because there are multiple relevant lambdas for a single collect call). We do also handle anonymous inner classes. I only added support for collecting into toMap for now; I'm not sure if there are other important cases.

I did a couple drive-by refactorings in this PR as I couldn't help it. I can undo them if they really make review more difficult, but I hope it's ok.

codecov · 2024-03-22T22:57:09Z

Codecov Report

Attention: Patch coverage is 96.51163% with 3 lines in your changes are missing coverage. Please review.

Project coverage is 87.13%. Comparing base (ce892d7) to head (3d985b7).

Files	Patch %	Lines
...nullaway/handlers/StreamNullabilityPropagator.java	95.16%	0 Missing and 3 partials ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master     #938      +/-   ##
============================================
+ Coverage     87.04%   87.13%   +0.08%     
- Complexity     1995     2011      +16     
============================================
  Files            77       78       +1     
  Lines          6447     6513      +66     
  Branches       1252     1264      +12     
============================================
+ Hits           5612     5675      +63     
  Misses          422      422              
- Partials        413      416       +3

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lazaroclapp

Approach makes sense to me, mostly a few requests to update the docs :)

lazaroclapp · 2024-03-23T21:48:45Z

nullaway/src/main/java/com/uber/nullaway/handlers/StreamNullabilityPropagatorFactory.java

+                "<T,K,U>toMap(java.util.function.Function<? super T,? extends K>,java.util.function.Function<? super T,? extends U>)",
+                ImmutableSet.of(0, 1),
+                "apply",
+                ImmutableSet.of(0))


Does Rx have an equivalent? See getRxStreamNullabilityPropagator()

RxJava 3 does have an Observable.collect method that takes a Collector:

http://reactivex.io/RxJava/3.x/javadoc/io/reactivex/rxjava3/core/Observable.html#collect-java.util.stream.Collector-

And there was a previous collect API that acts like reduce or fold where this support may be relevant. But I'd rather address our immediate need in this PR, and maybe file a follow-up task on systematically going through the Stream and RxJava APIs to add support for further methods. Sound ok?

lazaroclapp · 2024-03-23T21:51:33Z

nullaway/src/main/java/com/uber/nullaway/handlers/stream/StreamModelBuilder.java

+    return this;
+  }
+
+  public StreamModelBuilder withCollectMethodFromSignature(


Javadoc, please, specially because this has a lot of arguments with complex to understand semantics (e.g. argsToCollectorFactoryMethod vs argsToCollectorFactoryMethod). An example in the docs might even be a good idea :)

Edit: After reading a bit more, an alternative is to link to the docs on CollectLikeMethodRecord, but I also wouldn't mind a bit of redundant documentation of this arguments here.

nullaway/src/main/java/com/uber/nullaway/handlers/stream/StreamTypeRecord.java

lazaroclapp · 2024-03-23T22:09:54Z

nullaway/src/main/java/com/uber/nullaway/handlers/StreamNullabilityPropagator.java

+              streamType.getCollectlikeMethodRecord(methodSymbol);
+          if (collectlikeMethodRecord != null && methodSymbol.getParameters().length() == 1) {
+            handleCollectCall(tree, collectlikeMethodRecord);
+          }


Not for this PR, but wonder if as a follow up you want to extract the other two cases of this if into their own methods too, with onMatchMethodInvocation(...) as just a dispatcher.

Opened #944 to keep this PR simpler

lazaroclapp · 2024-03-23T22:12:29Z

nullaway/src/main/java/com/uber/nullaway/handlers/StreamNullabilityPropagator.java

+
+  /**
+   * Handles a call to a collect-like method. If the argument to the method is supported, updates
+   * the {@link #collectCallToInnerMethodsOrLambdas} map appropriately.


Adding a description of the arguments here would make this method easier to follow. What method invocation is tree referring to on entry? (collect(...) itself, I presume)

lazaroclapp · 2024-03-23T22:14:06Z

nullaway/src/main/java/com/uber/nullaway/handlers/StreamNullabilityPropagator.java

+      MethodInvocationTree tree, CollectLikeMethodRecord collectlikeMethodRecord) {
+    ExpressionTree argTree = tree.getArguments().get(0);
+    if (argTree instanceof MethodInvocationTree) {
+      MethodInvocationTree collectInvokeArg = (MethodInvocationTree) argTree;


This one is the Collectors.toMap(...) invocation, right?

Yup, 8b3f984

lazaroclapp · 2024-03-23T22:25:51Z

nullaway/src/main/java/com/uber/nullaway/handlers/StreamNullabilityPropagator.java

Not required, but should we update the docs in lines 74-100 and the list of examples in the docs for observableCallToInnerMethodOrLambda to include info on .collect() calls?

Added a few lines in 8b3f984

lazaroclapp · 2024-03-23T22:29:25Z

nullaway/src/main/java/com/uber/nullaway/handlers/StreamNullabilityPropagator.java

+      LinkedHashMultimap.create();
+
+  // Map from map or collect method (or lambda) to corresponding previous filter method (e.g.
+  // B.apply => A.filter)


Probably need an example here for the collect case, specially if we update the global docs above.

msridhar · 2024-03-26T17:18:05Z

@lazaroclapp this is ready for another look. I added support for a couple more collector factory methods based on feedback in #934 (comment). This required some generalization, as we couldn't support multiple factory methods for a single collect method before; see d317d0e and c6ac215. But the overall logical structure is the same.

lazaroclapp

LGTM. One minor comment about a potential refactoring, but entirely up to you at this point :)

nullaway/src/main/java/com/uber/nullaway/handlers/StreamNullabilityPropagator.java

msridhar added 7 commits March 22, 2024 13:21

test

68d5fcd

WIP

94639cc

Merge branch 'master' into issue-934

dabd0f9

more

9959485

WIP

fc03dc4

fix cast

b747e93

fix and another test

aa99bd2

msridhar added 6 commits March 22, 2024 16:35

handle anonymous classes, more tests

96d057f

renaming and docs

cad63a0

rename

b473e5c

more refactoring and docs

ed01dcd

typo

363fc06

one more comment

30ecc4c

msridhar changed the title ~~[WIP] Collectors.toMap handling for streams~~ Collectors.toMap handling for streams Mar 23, 2024

msridhar marked this pull request as ready for review March 23, 2024 00:20

msridhar requested a review from lazaroclapp March 23, 2024 00:20

msridhar mentioned this pull request Mar 23, 2024

Control flow analysis fails within a stream collector #934

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lazaroclapp reviewed Mar 23, 2024

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msridhar added 2 commits March 26, 2024 08:45

Merge branch 'master' into issue-934

809c5d6

add docs

3923589

msridhar mentioned this pull request Mar 26, 2024

Extract methods in StreamNullabilityPropagator #944

Closed

msridhar added 6 commits March 26, 2024 09:15

docs and rename

2724339

more docs

8b3f984

docs

1b57a96

fix Javadoc error

ff1b191

Add support for Collectors.groupingBy; required some refactoring

d317d0e

Support toImmutableMap

c6ac215

msridhar requested a review from lazaroclapp March 26, 2024 17:16

Merge branch 'master' into issue-934

24b0275

lazaroclapp approved these changes Mar 27, 2024

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nullaway/src/main/java/com/uber/nullaway/handlers/StreamNullabilityPropagator.java Show resolved Hide resolved

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msridhar enabled auto-merge (squash) March 27, 2024 18:36

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msridhar merged commit 76f0f77 into uber:master Mar 27, 2024
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msridhar deleted the issue-934 branch March 27, 2024 18:43

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Collectors.toMap handling for streams #938

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`Collectors.toMap` handling for streams #938

`Collectors.toMap` handling for streams #938

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