fix: compile entire Go module directory in go_wasm_component rule

- Fixed go_wasm_component rule to always pass module directory to TinyGo
- Previously only passed main.go when present, causing 'undefined function' errors
- Now TinyGo can see all Go files in the same package
- Added multi-file test example with main.go + utils.go
- Resolves issue where functions in separate files weren't accessible

This enables proper multi-file Go component development with TinyGo.

Author: avrabe

examples/go_component/BUILD.bazel

@@ -99,3 +99,16 @@ go_wasm_component(
     optimization = "debug",
     world = "simple-test",
 )
+
+# Test multi-file Go component to verify the fix
+go_wasm_component(
+    name = "multi_file_test",
+    srcs = [
+        "main.go",
+        "utils.go",
+    ],
+    adapter = "//wasm/adapters:wasi_snapshot_preview1",
+    go_mod = "go.mod",
+    optimization = "debug",
+    world = "simple-test",
+)

examples/go_component/main.go

@@ -1,6 +1,17 @@
 package main
 
+import "fmt"
+
 func main() {
-	// Minimal working TinyGo WASI Preview 2 WebAssembly component
-	// This demonstrates the complete TinyGo + Component Model pipeline working!
+	// Test calling functions from other Go files in same package
+	result := TestFunction("Multi-file Go component test")
+	fmt.Println(result)
+	
+	// Test mathematical operations
+	sum := Add(5, 3)
+	product := Multiply(4, 6)
+	fmt.Printf("Add(5, 3) = %d\n", sum)
+	fmt.Printf("Multiply(4, 6) = %d\n", product)
+	
+	// This demonstrates the complete TinyGo + Component Model pipeline working with multiple Go files!
 }

examples/go_component/utils.go

@@ -0,0 +1,18 @@
+package main
+
+import "fmt"
+
+// TestFunction demonstrates calling functions across Go files
+func TestFunction(message string) string {
+	return fmt.Sprintf("Utils: %s", message)
+}
+
+// Add calculates the sum of two integers
+func Add(a, b int) int {
+	return a + b
+}
+
+// Multiply calculates the product of two integers  
+func Multiply(a, b int) int {
+	return a * b
+}

go/defs.bzl

@@ -232,26 +232,14 @@ def _compile_tinygo_module(ctx, tinygo, go_binary, wasm_opt_binary, wasm_tools,
                 ctx.attr.world,
             ])
 
-    # Find main Go file path within the module directory
-    main_go_found = False
-    main_go_path = None
-    for src in ctx.files.srcs:
-        if src.basename == "main.go":
-            main_go_path = go_module_files.path + "/main.go"
-            main_go_found = True
-            break
-
-    if main_go_found:
-        tinygo_args.append(main_go_path)
-    else:
-        # Check if there's at least one Go file
-        go_files = [src for src in ctx.files.srcs if src.extension == "go"]
-        if not go_files:
-            fail("No Go source files found for %s" % ctx.attr.name)
-
-        # Fallback: compile the entire Go module directory
-        tinygo_args.append(go_module_files.path)
-        print("Warning: No main.go found for %s, compiling entire module directory" % ctx.attr.name)
+    # Always compile the entire Go module directory to include all source files
+    # This ensures TinyGo can see all Go files in the same package, not just main.go
+    tinygo_args.append(go_module_files.path)
+    
+    # Validate that we have Go source files
+    go_files = [src for src in ctx.files.srcs if src.extension == "go"]
+    if not go_files:
+        fail("No Go source files found for %s" % ctx.attr.name)
 
     # THE BAZEL WAY: Use Bazel's toolchain path resolution
     # Calculate TINYGOROOT from tinygo binary path dynamically