Fix platform issue when determining module name from file (#1505)

CHANGELOG.next.toml

@@ -27,3 +27,9 @@ message = "Add comments for docker settings needed when using this sdk"
 references = ["aws-sdk-rust#540"]
 meta = { "breaking" = false, "tada" = false, "bug" = false }
 author = "jmklix"
+
+[[smithy-rs]]
+message = "Fix issue with codegen on Windows where module names were incorrectly determined from filenames"
+references = ["smithy-rs#1505"]
+meta = { "breaking" = false, "tada" = false, "bug" = true }
+author = "kiiadi"

codegen/src/main/kotlin/software/amazon/smithy/rust/codegen/rustlang/RustWriter.kt

@@ -24,6 +24,7 @@ import software.amazon.smithy.rust.codegen.smithy.isOptional
 import software.amazon.smithy.rust.codegen.smithy.rustType
 import software.amazon.smithy.rust.codegen.util.orNull
 import software.amazon.smithy.utils.AbstractCodeWriter
+import java.io.File
 import java.util.function.BiFunction
 
 /**
@@ -393,7 +394,7 @@ class RustWriter private constructor(
     }
 
     fun module(): String? = if (filename.startsWith("src") && filename.endsWith(".rs")) {
-        filename.removeSuffix(".rs").split('/').last()
+        filename.removeSuffix(".rs").substringAfterLast(File.separatorChar)
     } else null
 
     fun safeName(prefix: String = "var"): String {

codegen/src/test/kotlin/software/amazon/smithy/rust/lang/RustWriterTest.kt

@@ -143,4 +143,10 @@ class RustWriterTest {
         )
         sut.toString().shouldContain("inner: hello, regular: http::foo")
     }
+
+    @Test
+    fun `can handle file paths properly when determining module`() {
+        val sut = RustWriter.forModule("src/module_name")
+        sut.module().shouldBe("module_name")
+    }
 }