Fix java getter / setter name generation (#2356)

Kotlin has special rules for conversion around properties that start with "is" 
For more info see:
https://kotlinlang.org/docs/java-interop.html#getters-and-setters
https://kotlinlang.org/docs/java-to-kotlin-interop.html#properties

2 files changed, 136 insertions, 2 deletions

diff --git a/plugins/base/src/main/kotlin/translators/descriptors/DefaultDescriptorToDocumentableTranslator.kt b/plugins/base/src/main/kotlin/translators/descriptors/DefaultDescriptorToDocumentableTranslator.kt
index 96bd2fc0..f636f984 100644
--- a/plugins/base/src/main/kotlin/translators/descriptors/DefaultDescriptorToDocumentableTranslator.kt
+++ b/plugins/base/src/main/kotlin/translators/descriptors/DefaultDescriptorToDocumentableTranslator.kt
@@ -616,9 +616,25 @@ private class DokkaDescriptorVisitor(
             )
 
         val name = run {
-            val modifier = if (isGetter) "get" else "set"
             val rawName = propertyDescriptor.name.asString()
-            "$modifier${rawName.capitalize()}"
+            /*
+             * Kotlin has special rules for conversion around properties that
+             * start with "is" For more info see:
+             * https://kotlinlang.org/docs/java-interop.html#getters-and-setters
+             * https://kotlinlang.org/docs/java-to-kotlin-interop.html#properties
+             *
+             * Based on our testing, this rule only applies when the letter after
+             * the "is" is *not* lowercase. This means that words like "issue" won't
+             * have the rule applied but "is_foobar" and "is1of" will have the rule applied.
+             */
+            val specialCaseIs = rawName.startsWith("is")
+                    && rawName.getOrNull(2)?.isLowerCase() == false
+
+            if (specialCaseIs) {
+                if (isGetter) rawName else rawName.replaceFirst("is", "set")
+            } else {
+                if (isGetter) "get${rawName.capitalize()}" else "set${rawName.capitalize()}"
+            }
         }
 
         val parameters =
diff --git a/plugins/base/src/test/kotlin/translators/AccessorMethodNamingTest.kt b/plugins/base/src/test/kotlin/translators/AccessorMethodNamingTest.kt
new file mode 100644
index 00000000..aeea194f
--- /dev/null
+++ b/plugins/base/src/test/kotlin/translators/AccessorMethodNamingTest.kt
@@ -0,0 +1,118 @@
+package translators
+
+import org.junit.jupiter.api.Assertions.*
+import org.jetbrains.dokka.base.testApi.testRunner.BaseAbstractTest
+import org.jetbrains.dokka.model.DProperty
+import org.junit.jupiter.api.Test
+
+/**
+ * https://kotlinlang.org/docs/java-to-kotlin-interop.html#properties
+ * https://kotlinlang.org/docs/java-interop.html#getters-and-setters
+ */
+class AccessorMethodNamingTest : BaseAbstractTest() {
+
+    @Test
+    fun `standard property`() {
+        testAccessors("data class TestCase(var standardString: String, var standardBoolean: Boolean)") {
+            doTest("standardString", "getStandardString", "setStandardString")
+            doTest("standardBoolean", "getStandardBoolean", "setStandardBoolean")
+        }
+    }
+
+    @Test
+    fun `properties that start with the word 'is' use the special is rules`() {
+        testAccessors("data class TestCase(var isFoo: String, var isBar: Boolean)") {
+            doTest("isFoo", "isFoo", "setFoo")
+            doTest("isBar", "isBar", "setBar")
+        }
+    }
+
+    @Test
+    fun `properties that start with a word that starts with 'is' use get and set`() {
+        testAccessors("data class TestCase(var issuesFetched: Int, var issuesWereDisplayed: Boolean)") {
+            doTest("issuesFetched", "getIssuesFetched", "setIssuesFetched")
+            doTest("issuesWereDisplayed", "getIssuesWereDisplayed", "setIssuesWereDisplayed")
+        }
+    }
+
+    @Test
+    fun `properties that start with the word 'is' followed by underscore use the special is rules`() {
+        testAccessors("data class TestCase(var is_foo: String, var is_bar: Boolean)") {
+            doTest("is_foo", "is_foo", "set_foo")
+            doTest("is_bar", "is_bar", "set_bar")
+        }
+    }
+
+    @Test
+    fun `properties that start with the word 'is' followed by a number use the special is rules`() {
+        testAccessors("data class TestCase(var is1of: String, var is2of: Boolean)") {
+            doTest("is1of", "is1of", "set1of")
+            doTest("is2of", "is2of", "set2of")
+        }
+    }
+
+    @Test
+    fun `sanity check short names`() {
+        testAccessors(
+            """
+            data class TestCase(
+               var i: Boolean,
+               var `is`: Boolean,
+               var isz: Boolean,
+               var isA: Int,
+               var isB: Boolean,
+            )
+            """.trimIndent()
+        ) {
+            doTest("i", "getI", "setI")
+            doTest("is", "getIs", "setIs")
+            doTest("isz", "getIsz", "setIsz")
+            doTest("isA", "isA", "setA")
+            doTest("isB", "isB", "setB")
+        }
+    }
+
+    private fun testAccessors(code: String, block: PropertyTestCase.() -> Unit) {
+        val configuration = dokkaConfiguration {
+            suppressObviousFunctions = false
+            sourceSets {
+                sourceSet {
+                    sourceRoots = listOf("src/main/kotlin")
+                }
+            }
+        }
+
+        testInline("""
+            /src/main/kotlin/sample/TestCase.kt
+            package sample
+            
+            $code
+            """.trimIndent(),
+            configuration) {
+            documentablesMergingStage = { module ->
+                val properties = module.packages.single().classlikes.first().properties
+                PropertyTestCase(properties).apply {
+                    block()
+                    finish()
+                }
+            }
+        }
+    }
+
+    private class PropertyTestCase(private val properties: List<DProperty>) {
+        private var testsDone: Int = 0
+
+        fun doTest(kotlinName: String, getter: String? = null, setter: String? = null) {
+            properties.first { it.name == kotlinName }.let {
+                assertEquals(getter, it.getter?.name)
+                assertEquals(setter, it.setter?.name)
+            }
+            testsDone += 1
+        }
+
+        fun finish() {
+            assertTrue(testsDone > 0, "No tests in TestCase")
+            assertEquals(testsDone, properties.size)
+        }
+    }
+}
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