Paul King created GROOVY-12215:
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Summary: Fat-free variants for collectMany, countBy, split,
take/dropWhile, groupBy
Key: GROOVY-12215
URL: https://issues.apache.org/jira/browse/GROOVY-12215
Project: Groovy
Issue Type: Improvement
Reporter: Paul King
Assignee: Paul King
h3. Summary
Sub-task of GROOVY-12205. Adds the straightforward "fat-free"
functional-interface twins — a single {{java.util.function}} overload beside
each existing {{Closure}} overload — for the mapping/filtering DGM methods that
currently have none. These are mechanical, following the conventions
established in GROOVY-12054; no design decisions are involved.
h3. Methods
||Method||Closure overloads without a twin||Functional type||Receivers||
|{{collectMany}}|8|{{Function<? super E, ? extends Collection<? extends
T>>}}|Iterable (x2), Map (x2), Iterator (x2), {{E[]}} (x2)|
|{{collectingMany}}|1|{{Function}} (lazy)|Iterator|
|{{countBy}}|4|{{Function<? super E, ? extends K>}}|Iterable, Iterator, Map,
{{E[]}}|
|{{split}}|5|{{Predicate<? super T>}}|Object, Collection, List, Set, {{T[]}}|
|{{groupBy}} (single-key)|2|{{Function<? super T, ? extends K>}}|Map,
{{Object[]}} (the Iterable twin already exists)|
|{{takeWhile}}|6|{{Predicate<? super T>}}|List, Iterable, SortedSet, Map,
Iterator, {{T[]}}|
|{{dropWhile}}|6|{{Predicate<? super T>}}|SortedSet, List, Iterable, Map,
Iterator, {{T[]}}|
Total: 32 new overloads.
h3. Conventions (per GROOVY-12054)
* PECS wildcards on the functional parameter; {{@since 6.0.0}}.
* Inline javadoc example using {{<pre class="language-groovy
groovyTestCase">}}, cross-linking the {{Closure}} counterpart via {{@link}}.
* Plain single-SAM overloads only — *not* {{@Incubating}}; that annotation is
reserved for the curried {{(BiXxx, param)}} forms, which are a separate item.
h3. Exclusions
* {{groupBy}} multi-key forms ({{Object...}} / {{List<Closure>}}) — no clean
functional analogue.
* {{takeWhile}}/{{dropWhile}} on {{CharSequence}}/{{GString}} (the SGM
char-by-char forms) — a String-domain {{Predicate<Character>}}/{{IntPredicate}}
decision, out of scope for this collection-focused sub-task (keeps the count at
6 each).
h3. Compatibility
Existing closure/lambda call sites are unaffected: a {{Closure}} literal binds
to the {{Closure}} overload, while method references and typed functional
values select the twin under {{@CompileStatic}} (per GROOVY-12214). Only check:
an existing {{@CompileStatic}} call passing a literal {{null}} to one of these
currently-single-overload methods would become ambiguous — a rare,
grep-checkable case, resolved with a cast if found.
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