Narrow filtering of imports in modules (#26)

This ensures that when you have:

module/com/example/Foo
otherpackage/com/example/not_in_module/Bar

module's dependency on Bar isn't filtered out.

java/gazelle/generate.go

@@ -7,6 +7,7 @@ import (
 	"path/filepath"
 	"sort"
 	"strings"
+	"unicode"
 
 	"github.com/bazel-contrib/rules_jvm/java/gazelle/javaconfig"
 	"github.com/bazel-contrib/rules_jvm/java/gazelle/private/java"
@@ -234,7 +235,14 @@ func (l javaLang) generateModuleRoot(args language.GenerateArgs, cfg *javaconfig
 	filteredImports := filterImports(allImports, func(i string) bool {
 		for _, n := range allPackageNames {
 			if strings.HasPrefix(i, n) {
-				return false
+				// Assume the standard java convention of class names starting with upper case
+				// and package components starting with lower case.
+				// Without this check, one module with dependencies on a subpackage which _isn't_
+				// in the module won't be detected.
+				suffixRunes := []rune(i[len(n):])
+				if len(suffixRunes) >= 2 && suffixRunes[0] == '.' && unicode.IsUpper(suffixRunes[1]) {
+					return false
+				}
 			}
 		}
 		return true

java/gazelle/testdata/module-granularity/module1/BUILD.want

@@ -7,7 +7,10 @@ java_library(
         "src/main/java/com/example/hello/Hello.java",
         "src/main/java/com/example/hello/world/World.java",
     ],
-    _gazelle_imports = ["java.lang.String"],
+    _gazelle_imports = [
+        "com.example.hello.notworld.NotWorld",
+        "java.lang.String",
+    ],
     _java_packages = [
         "com.example.hello",
         "com.example.hello.world",

java/gazelle/testdata/module-granularity/module1/src/main/java/com/example/hello/Hello.java

@@ -1,10 +1,12 @@
 package com.example.hello;
 
 import com.example.hello.world.World;
+import com.example.hello.notworld.NotWorld;
 
 public class Hello {
     public static void main(String[] args) {
         World one = new World();
         System.out.printf("Hello, %s!", one.name);
+        System.out.printf("Hello also, %s!", NotWorld.NOT_WORLD);
     }
 }

java/gazelle/testdata/module-granularity/notmodule/src/main/java/com/example/hello/notworld/NotWorld.java

@@ -0,0 +1,5 @@
+package com.example.hello.notworld;
+
+public class NotWorld {
+  public static final String NOT_WORLD = "Not World!";
+}