Remove duplicated imports (OpenAPITools#1414)

* remove duplicated imports

* fix model import in java

* update generator docs

* fix model import for retrofit2 client

Author: wing328

modules/openapi-generator/src/main/java/org/openapitools/codegen/DefaultGenerator.java

@@ -1032,13 +1032,16 @@ private Map<String, Object> processOperations(CodegenConfig config, String tag,
         }
 
         List<Map<String, String>> imports = new ArrayList<Map<String, String>>();
+        Set<String> mappingSet = new TreeSet<>();
         for (String nextImport : allImports) {
             Map<String, String> im = new LinkedHashMap<String, String>();
             String mapping = config.importMapping().get(nextImport);
             if (mapping == null) {
                 mapping = config.toModelImport(nextImport);
             }
-            if (mapping != null) {
+
+            if (mapping != null && !mappingSet.contains(mapping)) { // ensure import (mapping) is unique
+                mappingSet.add(mapping);
                 im.put("import", mapping);
                 im.put("classname", nextImport);
                 if (!imports.contains(im)) { // avoid duplicates

modules/openapi-generator/src/main/resources/Java/JSON.mustache

@@ -25,9 +25,9 @@ import org.threeten.bp.OffsetDateTime;
 import org.threeten.bp.format.DateTimeFormatter;
 {{/threetenbp}}
 
-{{#parent.length}}
+{{#models.0}}
 import {{modelPackage}}.*;
-{{/parent.length}}
+{{/models.0}}
 import okio.ByteString;
 
 import java.io.IOException;

modules/openapi-generator/src/main/resources/Java/libraries/retrofit2/JSON.mustache

@@ -25,9 +25,9 @@ import org.threeten.bp.OffsetDateTime;
 import org.threeten.bp.format.DateTimeFormatter;
 {{/threetenbp}}
 
-{{#parent.length}}
+{{#models.0}}
 import {{modelPackage}}.*;
-{{/parent.length}}
+{{/models.0}}
 
 import java.io.IOException;
 import java.io.StringReader;

samples/client/petstore/lua/.openapi-generator/VERSION

@@ -1 +1 @@
-3.3.2-SNAPSHOT
+3.3.3-SNAPSHOT

samples/client/petstore/lua/petstore/api/pet_api.lua

@@ -18,7 +18,6 @@ local basexx = require "basexx"
 -- model import
 local petstore_api_response = require "petstore.model.api_response"
 local petstore_pet = require "petstore.model.pet"
-local petstore_pet = require "petstore.model.pet"
 
 local pet_api = {}
 local pet_api_mt = {

samples/client/petstore/lua/petstore/api/store_api.lua

@@ -17,7 +17,6 @@ local basexx = require "basexx"
 
 -- model import
 local petstore_order = require "petstore.model.order"
-local petstore_order = require "petstore.model.order"
 
 local store_api = {}
 local store_api_mt = {

samples/client/petstore/lua/petstore/api/user_api.lua

@@ -17,7 +17,6 @@ local basexx = require "basexx"
 
 -- model import
 local petstore_user = require "petstore.model.user"
-local petstore_user = require "petstore.model.user"
 
 local user_api = {}
 local user_api_mt = {