Prevent aliased imports from colliding with existing imports

Author: damianw

docs/changelog.md

@@ -4,6 +4,7 @@ Change Log
 ## Unreleased
 
 * Fix: Support delegates on anonymous classes. (#2034)
+* Fix: Prevent aliased imports from colliding with existing imports (#2046)
 
 ## Version 2.0.0
 

kotlinpoet/src/jvmMain/kotlin/com/squareup/kotlinpoet/CodeWriter.kt

@@ -405,6 +405,7 @@ internal class CodeWriter(
         implicitModifiers = if (omitImplicitModifiers) emptySet() else setOf(KModifier.PUBLIC),
         includeKdocTags = true,
       )
+
       is TypeAliasSpec -> o.emit(this)
       is CodeBlock -> emitCode(o, isConstantContext = isConstantContext)
       else -> emit(o.toString())
@@ -751,7 +752,7 @@ internal class CodeWriter(
       val imported = mutableMapOf<String, Set<T>>()
       forEach { (simpleName, qualifiedNames) ->
         val canonicalNamesToQualifiedNames = qualifiedNames.associateBy { it.computeCanonicalName() }
-        if (canonicalNamesToQualifiedNames.size == 1 && simpleName !in referencedNames) {
+        if (canonicalNamesToQualifiedNames.size == 1 && simpleName !in referencedNames && simpleName !in imported) {
           val canonicalName = canonicalNamesToQualifiedNames.keys.single()
           generatedImports[canonicalName] = Import(canonicalName)
 
@@ -760,7 +761,7 @@ internal class CodeWriter(
           // functions declared in the same package. In these cases, a single import will suffice for all of them.
           imported[simpleName] = qualifiedNames
         } else {
-          generateImportAliases(simpleName, canonicalNamesToQualifiedNames, capitalizeAliases)
+          generateImportAliases(simpleName, canonicalNamesToQualifiedNames, capitalizeAliases, imported.keys)
             .onEach { (a, qualifiedName) ->
               val alias = a.escapeAsAlias()
               val canonicalName = qualifiedName.computeCanonicalName()
@@ -777,24 +778,33 @@ internal class CodeWriter(
       simpleName: String,
       canonicalNamesToQualifiedNames: Map<String, T>,
       capitalizeAliases: Boolean,
+      imported: Set<String>,
     ): List<Pair<String, T>> {
       val canonicalNameSegmentsToQualifiedNames = canonicalNamesToQualifiedNames.mapKeys { (canonicalName, _) ->
         canonicalName.split('.')
           .dropLast(1) // Last segment of the canonical name is the simple name, drop it to avoid repetition.
           .filter { it != "Companion" }
           .map { it.replaceFirstChar(Char::uppercaseChar) }
       }
+      val minimumNumberOfSegments = canonicalNameSegmentsToQualifiedNames.keys.minOf { it.size }
       val aliasNames = mutableMapOf<String, T>()
       var segmentsToUse = 0
       // Iterate until we have unique aliases for all names.
-      while (aliasNames.size != canonicalNamesToQualifiedNames.size) {
+      outer@ while (aliasNames.size != canonicalNamesToQualifiedNames.size) {
         segmentsToUse += 1
         aliasNames.clear()
         for ((segments, qualifiedName) in canonicalNameSegmentsToQualifiedNames) {
           val aliasPrefix = segments.takeLast(min(segmentsToUse, segments.size))
             .joinToString(separator = "")
             .replaceFirstChar { if (!capitalizeAliases) it.lowercaseChar() else it }
-          val aliasName = aliasPrefix + simpleName.replaceFirstChar(Char::uppercaseChar)
+          val aliasSuffix = "_".repeat(segmentsToUse - segments.size)
+          val aliasName = aliasPrefix + simpleName.replaceFirstChar(Char::uppercaseChar) + aliasSuffix
+          // If this name has already been imported (e.g. a regular import already exists with this name),
+          // continue trying with a greater number of segments.
+          if (aliasName in imported) {
+            aliasNames.clear()
+            continue@outer
+          }
           aliasNames[aliasName] = qualifiedName
         }
       }

kotlinpoet/src/jvmTest/kotlin/com/squareup/kotlinpoet/KotlinPoetTest.kt

@@ -1489,4 +1489,111 @@ class KotlinPoetTest {
       """.trimMargin(),
     )
   }
+
+  // https://github.com/square/kotlinpoet/issues/2046
+  @Test fun importAliasCollisionWithRegularImportWhenAliasesComputedFirst() {
+    val class1 = ClassName("com.squareup.taco", "Meal")
+    val class2 = ClassName("com.squareup.burrito", "Meal")
+    val class3 = ClassName("com.squareup.meal", "TacoMeal")
+    val source = FileSpec.builder("com.squareup.food", "Food")
+      .addType(
+        TypeSpec.classBuilder("Food")
+          .addProperty("tacoPackageMeal", class1)
+          .addProperty("burritoPackageMeal", class2)
+          .addProperty("mealPackageTacoMeal", class3)
+          .build(),
+      )
+      .build()
+    assertThat(source.toString()).isEqualTo(
+      """
+        |package com.squareup.food
+        |
+        |import com.squareup.burrito.Meal as BurritoMeal
+        |import com.squareup.meal.TacoMeal as MealTacoMeal
+        |import com.squareup.taco.Meal as TacoMeal
+        |
+        |public class Food {
+        |  public val tacoPackageMeal: TacoMeal
+        |
+        |  public val burritoPackageMeal: BurritoMeal
+        |
+        |  public val mealPackageTacoMeal: MealTacoMeal
+        |}
+        |
+      """.trimMargin(),
+    )
+  }
+
+  // https://github.com/square/kotlinpoet/issues/2046
+  @Test fun importAliasCollisionWithImportWhenRegularImportComputedFirst() {
+    val class1 = ClassName("com.squareup.taco", "Meal")
+    val class2 = ClassName("com.squareup.burrito", "Meal")
+    val class3 = ClassName("com.squareup.meal", "TacoMeal")
+    val source = FileSpec.builder("com.squareup.food", "Food")
+      .addType(
+        TypeSpec.classBuilder("Food")
+          .addProperty("mealPackageTacoMeal", class3)
+          .addProperty("tacoPackageMeal", class1)
+          .addProperty("burritoPackageMeal", class2)
+          .build(),
+      )
+      .build()
+    assertThat(source.toString()).isEqualTo(
+      """
+        |package com.squareup.food
+        |
+        |import com.squareup.meal.TacoMeal
+        |import com.squareup.burrito.Meal as SquareupBurritoMeal
+        |import com.squareup.taco.Meal as SquareupTacoMeal
+        |
+        |public class Food {
+        |  public val mealPackageTacoMeal: TacoMeal
+        |
+        |  public val tacoPackageMeal: SquareupTacoMeal
+        |
+        |  public val burritoPackageMeal: SquareupBurritoMeal
+        |}
+        |
+      """.trimMargin(),
+    )
+  }
+
+  // https://github.com/square/kotlinpoet/issues/2046
+  @Test fun importAliasCollisionWithImportWhenWeRunOutOfSegments() {
+    val class0 = ClassName("squareup", "SquareupTacoMeal")
+    val class1 = ClassName("squareup.taco", "Meal")
+    val class2 = ClassName("squareup.burrito", "Meal")
+    val class3 = ClassName("squareup", "TacoMeal")
+    val source = FileSpec.builder("squareup.food", "Food")
+      .addType(
+        TypeSpec.classBuilder("Food")
+          .addProperty("noMoreSegments", class0)
+          .addProperty("mealPackageTacoMeal", class3)
+          .addProperty("tacoPackageMeal", class1)
+          .addProperty("burritoPackageMeal", class2)
+          .build(),
+      )
+      .build()
+    assertThat(source.toString()).isEqualTo(
+      """
+        |package squareup.food
+        |
+        |import squareup.SquareupTacoMeal
+        |import squareup.TacoMeal
+        |import squareup.burrito.Meal as SquareupBurritoMeal_
+        |import squareup.taco.Meal as SquareupTacoMeal_
+        |
+        |public class Food {
+        |  public val noMoreSegments: SquareupTacoMeal
+        |
+        |  public val mealPackageTacoMeal: TacoMeal
+        |
+        |  public val tacoPackageMeal: SquareupTacoMeal_
+        |
+        |  public val burritoPackageMeal: SquareupBurritoMeal_
+        |}
+        |
+      """.trimMargin(),
+    )
+  }
 }