Implement a rule to lint enum entry name (#638)

* Implement a rule to lint enum entry name

* Disable auto format for enum entry name for now

* Ignore formatting test

ktlint-ruleset-experimental/src/main/kotlin/com/pinterest/ktlint/ruleset/experimental/EnumEntryNameCaseRule.kt

@@ -0,0 +1,59 @@
+package com.pinterest.ktlint.ruleset.experimental
+
+import com.pinterest.ktlint.core.Rule
+import org.jetbrains.kotlin.com.intellij.lang.ASTNode
+import org.jetbrains.kotlin.com.intellij.psi.impl.source.tree.CompositeElement
+import org.jetbrains.kotlin.psi.KtEnumEntry
+
+class EnumEntryNameCaseRule : Rule("enum-entry-name-case") {
+
+    companion object {
+        const val ERROR_MESSAGE = "Enum entry name should be uppercase underscore-separated names like \"ENUM_ENTRY\" or upper camel-case like \"EnumEntry\""
+    }
+
+    override fun visit(
+        node: ASTNode,
+        autoCorrect: Boolean,
+        emit: (offset: Int, errorMessage: String, canBeAutoCorrected: Boolean) -> Unit
+    ) {
+        if (node !is CompositeElement) {
+            return
+        }
+        val enumEntry = node.psi as? KtEnumEntry ?: return
+        val name = enumEntry.name ?: return
+
+        if (name.containsLowerCase()) {
+            // In case of lower camel case like "enumName", or all lower case like "enumname"
+            if (!name.startsWithUpperCase()) {
+                emit(
+                    node.startOffset,
+                    ERROR_MESSAGE, false
+                )
+
+                if (autoCorrect) correct(enumEntry, name)
+            }
+
+            // In case of lower case with underscore like "enum_name"
+            else if (name.contains("_") && name.containsLowerCase()) {
+                emit(
+                    node.startOffset,
+                    ERROR_MESSAGE, false
+                )
+
+                if (autoCorrect) correct(enumEntry, name)
+            }
+        }
+    }
+
+    private fun correct(enumEntry: KtEnumEntry, originalName: String) {
+        enumEntry.setName(originalName.toUpperCase())
+    }
+
+    private fun String.startsWithUpperCase(): Boolean {
+        return this.isNotEmpty() && this[0].isUpperCase()
+    }
+
+    private fun String.containsLowerCase(): Boolean {
+        return this.any { it.isLowerCase() }
+    }
+}

ktlint-ruleset-experimental/src/main/kotlin/com/pinterest/ktlint/ruleset/experimental/ExperimentalRuleSetProvider.kt

@@ -11,6 +11,7 @@ class ExperimentalRuleSetProvider : RuleSetProvider {
         IndentationRule(),
         MultiLineIfElseRule(),
         NoEmptyFirstLineInMethodBlockRule(),
-        PackageNameRule()
+        PackageNameRule(),
+        EnumEntryNameCaseRule()
     )
 }

ktlint-ruleset-experimental/src/test/kotlin/com/pinterest/ktlint/ruleset/experimental/EnumEntryNameCaseRuleTest.kt

@@ -0,0 +1,58 @@
+package com.pinterest.ktlint.ruleset.experimental
+
+import com.pinterest.ktlint.core.LintError
+import com.pinterest.ktlint.test.format
+import com.pinterest.ktlint.test.lint
+import org.assertj.core.api.Assertions.assertThat
+import org.junit.Ignore
+import org.junit.Test
+
+class EnumEntryNameCaseRuleTest {
+
+    @Test
+    fun testFormatIsCorrect() {
+        val formatted =
+            """
+            enum class FirstEnum {
+                ENUM_ENTRY
+            }
+            enum class SecondEnum {
+                EnumEntry
+            }
+            """.trimIndent()
+
+        assertThat(EnumEntryNameCaseRule().lint(formatted)).isEmpty()
+        assertThat(EnumEntryNameCaseRule().format(formatted)).isEqualTo(formatted)
+    }
+
+    @Test
+    @Ignore("https://github.com/pinterest/ktlint/pull/638#issuecomment-558119749")
+    fun testFormat() {
+        val unformatted =
+            """
+            enum class FirstEnum {
+                enumEntry
+            }
+            enum class SecondEnum {
+                enum_entry
+            }
+            """.trimIndent()
+        val formatted =
+            """
+            enum class FirstEnum {
+                ENUMENTRY
+            }
+            enum class SecondEnum {
+                ENUM_ENTRY
+            }
+            """.trimIndent()
+
+        assertThat(EnumEntryNameCaseRule().lint(unformatted)).isEqualTo(
+            listOf(
+                LintError(2, 5, "enum-entry-name-case", EnumEntryNameCaseRule.ERROR_MESSAGE),
+                LintError(5, 5, "enum-entry-name-case", EnumEntryNameCaseRule.ERROR_MESSAGE)
+            )
+        )
+        assertThat(EnumEntryNameCaseRule().format(unformatted)).isEqualTo(formatted)
+    }
+}