fix: enable TinyGo custom WIT worlds and re-enable Go components in CI

- Fix TinyGo flag format: --wit-package/-world → -wit-package/-world
- Pass full WIT directory with deps/ structure for dependency resolution
- Add missing WASI imports required by TinyGo runtime (random, environment, monotonic-clock)
- Add WASI 0.2.0 dependencies: filesystem, sockets, random
- Fix calculator_with_bindings.go type mismatches and missing cm import
- Re-enable Go calculator components in CI (Linux & macOS)
- Document TinyGo WASI runtime requirement in README
- Enhance wit_structure tool for transitive deps copying

Fixes #80, #82

Author: avrabe

.github/workflows/ci.yml

@@ -106,6 +106,10 @@ jobs:
             //examples/go_component:calculator_component_debug \
             //examples/go_component:calculator_docs \
             //examples/go_component:calculator_manual \
+            //examples/go_component:calculator_component \
+            //examples/go_component:calculator_simple \
+            //examples/go_component:calculator_with_bindings \
+            //examples/go_component:calculator_simple_binding \
             //examples/go_component:http_service_component \
             //examples/go_component:http_service_docs \
             //examples/go_component:multi_file_test \
@@ -130,11 +134,6 @@ jobs:
             //tools/... \
             //providers/... \
             //test/go/... \
-            -//test/go:test_calculator_component_provides_info \
-            -//test/go:test_calculator_component_valid_wasm \
-            -//test/go:test_calculator_exports_verification \
-            -//test/go:all_go_tests \
-            -//test/go:go_component_tests \
             -//test/go:go_integration_tests \
             //test/cpp/... \
             //test/unit/... \
@@ -211,6 +210,10 @@ jobs:
             //examples/go_component:calculator_component_debug \
             //examples/go_component:calculator_docs \
             //examples/go_component:calculator_manual \
+            //examples/go_component:calculator_component \
+            //examples/go_component:calculator_simple \
+            //examples/go_component:calculator_with_bindings \
+            //examples/go_component:calculator_simple_binding \
             //examples/go_component:http_service_component \
             //examples/go_component:http_service_docs \
             //examples/go_component:multi_file_test \
@@ -235,11 +238,6 @@ jobs:
             //tools/... \
             //providers/... \
             //test/go/... \
-            -//test/go:test_calculator_component_provides_info \
-            -//test/go:test_calculator_component_valid_wasm \
-            -//test/go:test_calculator_exports_verification \
-            -//test/go:all_go_tests \
-            -//test/go:go_component_tests \
             -//test/go:go_integration_tests \
             //test/cpp/... \
             //test/unit/... \

MODULE.bazel

@@ -66,7 +66,7 @@ register_toolchains("@go_toolchains//:all")
 # WASI WIT interface definitions
 wasi_wit_ext = use_extension("//wasm:extensions.bzl", "wasi_wit")
 wasi_wit_ext.init()
-use_repo(wasi_wit_ext, "wasi_cli", "wasi_cli_v020", "wasi_clocks", "wasi_clocks_v020", "wasi_filesystem", "wasi_http", "wasi_io", "wasi_io_v020", "wasi_nn", "wasi_nn_v0_2_0_rc_2024_06_25", "wasi_nn_v0_2_0_rc_2024_08_19", "wasi_random", "wasi_sockets")  # Complete WASI ecosystem (0.2.3 + 0.2.0 + all NN versions)
+use_repo(wasi_wit_ext, "wasi_cli", "wasi_cli_v020", "wasi_clocks", "wasi_clocks_v020", "wasi_filesystem", "wasi_filesystem_v020", "wasi_http", "wasi_io", "wasi_io_v020", "wasi_nn", "wasi_nn_v0_2_0_rc_2024_06_25", "wasi_nn_v0_2_0_rc_2024_08_19", "wasi_random", "wasi_random_v020", "wasi_sockets", "wasi_sockets_v020")  # Complete WASI ecosystem (0.2.3 + 0.2.0 + all NN versions)
 
 # WebAssembly toolchains
 wasm_toolchain = use_extension("//wasm:extensions.bzl", "wasm_toolchain")

MODULE.bazel.lock

@@ -17,14 +17,28 @@ wit_library(
     name = "calculator_wit",
     srcs = ["wit/calculator.wit"],
     world = "calculator-world",
-    deps = ["@wasi_io_v020//:streams"],  # Add WASI IO 0.2.0 dependency required by TinyGo
+    deps = [
+        "@wasi_io_v020//:streams",
+        "@wasi_cli_v020//:cli",
+        "@wasi_clocks_v020//:clocks",
+        "@wasi_filesystem_v020//:filesystem",
+        "@wasi_random_v020//:random",
+    ],
 )
 
-# Simple calculator WIT - pure interface, TinyGo handles WASI internally
+# Simple calculator WIT - reactor mode with TinyGo-required WASI imports
+# TinyGo runtime needs these even for empty main() reactor components
 wit_library(
     name = "simple_calculator_wit",
     srcs = ["wit/simple-calculator.wit"],
     world = "calculator-world",
+    deps = [
+        "@wasi_io_v020//:streams",
+        "@wasi_cli_v020//:cli",
+        "@wasi_clocks_v020//:clocks",
+        "@wasi_filesystem_v020//:filesystem",
+        "@wasi_random_v020//:random",
+    ],
 )
 
 # WIT library definitions for HTTP service interface
@@ -176,3 +190,15 @@ go_wasm_component(
     optimization = "debug",
     world = "wasi:cli/command",
 )
+
+# Pure reactor component - NO main() function, NO WASI imports
+# This demonstrates the proper way to build Go library components
+go_wasm_component(
+    name = "calculator_reactor",
+    srcs = ["calculator_reactor.go"],
+    go_mod = "go.mod",
+    go_sum = "go.sum",
+    optimization = "release",
+    wit = ":simple_calculator_wit",
+    world = "calculator-world",
+)

examples/go_component/BUILD.bazel

@@ -107,6 +107,90 @@ go_wasm_component(
 - **Composability**: Link multiple components together
 - **Language Interop**: Call between Go, Rust, C++, JavaScript components
 
+## TinyGo WASI Runtime Requirement
+
+### Why TinyGo Components Always Need WASI
+
+Unlike C/C++ or Rust, **TinyGo reactor components (even with empty `main()`) require WASI imports**. This is due to TinyGo's Go runtime architecture, not a Component Model limitation.
+
+**TinyGo Runtime Architecture:**
+- TinyGo's Go runtime is built on WASI primitives for system operations
+- Even reactor components with `func main() {}` trigger runtime initialization
+- Runtime initialization performs memory management, goroutine setup, and I/O configuration
+- This is an architectural decision in TinyGo's design
+
+**Required WASI Imports:**
+
+All TinyGo components (both command and reactor) require these WASI Preview 2 interfaces:
+
+```wit
+world tinygo-component {
+    // I/O streams for runtime initialization
+    import wasi:io/[email protected];
+
+    // CLI interfaces for stdout/stderr/stdin
+    import wasi:cli/[email protected];
+    import wasi:cli/[email protected];
+    import wasi:cli/[email protected];
+
+    // Clock for time operations (time.Now(), etc.)
+    import wasi:clocks/[email protected];
+
+    // Filesystem for runtime initialization
+    import wasi:filesystem/[email protected];
+    import wasi:filesystem/[email protected];
+
+    // Your component's exports
+    export my-interface;
+}
+```
+
+**Contrast with Other Languages:**
+
+| Language | Pure Reactor (No WASI) | Why? |
+|----------|------------------------|------|
+| C/C++    | ✅ Possible | Can compile with `-nostdlib`, no runtime dependencies |
+| Rust     | ✅ Possible | `#![no_std]` removes runtime, pure library mode |
+| **TinyGo** | ❌ Not Possible | Runtime always initializes with WASI dependencies |
+
+**What TinyGo's Compiler Generates:**
+
+Even for a minimal reactor component:
+```go
+package main
+
+func main() {}  // Empty, reactor mode
+
+//export my_function
+func my_function() int32 {
+    return 42
+}
+```
+
+The TinyGo compiler still generates:
+1. Runtime initialization code that calls WASI filesystem APIs
+2. I/O stream setup for panic/error handling
+3. Clock initialization for time operations
+4. Memory allocator setup using WASI primitives
+
+**Practical Implications:**
+
+- **Component Composition**: Your Go component will have WASI import requirements
+- **Host Requirements**: The runtime (wasmtime, wasmer) must provide WASI Preview 2
+- **Performance**: The imports are lightweight and don't impact performance significantly
+- **Deployment**: This is transparent in most scenarios - modern runtimes provide WASI by default
+
+**No Workarounds Available:**
+
+There are no practical workarounds. TinyGo components always require WASI. However:
+- Most component hosts (wasmtime, wasmer, etc.) provide WASI Preview 2 by default
+- The WASI overhead is minimal and doesn't affect component composability
+- This is a known and accepted characteristic of TinyGo's design
+
+**Upstream Tracking:**
+
+See [TinyGo Issue #2703](https://github.com/tinygo-org/tinygo/issues/2703) for discussions about making the runtime more modular.
+
 ## Testing Components
 
 ```bash

examples/go_component/README.md

@@ -0,0 +1,45 @@
+// Package main provides a pure reactor WebAssembly component
+// Reactor components use package "main" but with an EMPTY main() function
+// This is the TinyGo way to build library components (see TinyGo issue #2703)
+package main
+
+// Pure export functions for WIT component interface
+// TinyGo will generate proper component exports via -wit-world flag
+
+//export example_calculator_add
+func add(a, b float64) float64 {
+	return a + b
+}
+
+//export example_calculator_subtract
+func subtract(a, b float64) float64 {
+	return a - b
+}
+
+//export example_calculator_multiply
+func multiply(a, b float64) float64 {
+	return a * b
+}
+
+//export example_calculator_divide
+func divide(a, b float64) float64 {
+	// In a real implementation, this would use WIT result type for error handling
+	// For this simple demo, division by zero returns 0
+	if b == 0 {
+		return 0
+	}
+	return a / b
+}
+
+// EMPTY main() for reactor mode
+// This tells TinyGo we want a reactor component, not a command component
+// The runtime is initialized in _initialize, not _start
+func main() {
+	// Reactor component - no main execution needed
+}
+
+// Prevent compiler from removing exports
+var _ = add
+var _ = subtract
+var _ = multiply
+var _ = divide

examples/go_component/calculator_reactor.go

@@ -3,6 +3,7 @@ package main
 import (
 	// The generated bindings will be at this path
 	"example.com/calculator/example/calculator/calculator"
+	"go.bytecodealliance.org/cm"
 )
 
 // Initialize the calculator component exports with generated bindings
@@ -20,12 +21,20 @@ func init() {
 		return a * b
 	}
 
-	calculator.Exports.Divide = func(a, b float64) float64 {
+	calculator.Exports.Divide = func(a, b float64) calculator.CalculationResult {
 		if b == 0 {
-			// Return NaN for division by zero
-			return 0.0 / 0.0
+			return calculator.CalculationResult{
+				Success: false,
+				Error:   cm.Some("division by zero"),
+				Value:   cm.None[float64](),
+			}
+		}
+		result := a / b
+		return calculator.CalculationResult{
+			Success: true,
+			Error:   cm.None[string](),
+			Value:   cm.Some(result),
 		}
-		return a / b
 	}
 
 	calculator.Exports.Calculate = func(operation calculator.Operation) calculator.CalculationResult {

examples/go_component/calculator_with_bindings.go

@@ -36,8 +36,19 @@ interface calculator {
 }
 
 world calculator-world {
-    /// Import WASI interfaces required by TinyGo stdlib
+    /// Import WASI interfaces required by TinyGo runtime
+    /// TinyGo's Go runtime requires these even for reactor components
+    /// This is a TinyGo architecture requirement, not a Component Model limitation
     import wasi:io/streams@0.2.0;
+    import wasi:cli/stdout@0.2.0;
+    import wasi:cli/stderr@0.2.0;
+    import wasi:cli/stdin@0.2.0;
+    import wasi:cli/environment@0.2.0;
+    import wasi:clocks/wall-clock@0.2.0;
+    import wasi:clocks/monotonic-clock@0.2.0;
+    import wasi:filesystem/types@0.2.0;
+    import wasi:filesystem/preopens@0.2.0;
+    import wasi:random/random@0.2.0;
 
     export calculator;
 }

examples/go_component/wit/calculator.wit

@@ -7,6 +7,19 @@ interface calculator {
     divide: func(a: f64, b: f64) -> f64;
 }
 
+/// Reactor world - WASI imports required by TinyGo runtime
+/// TinyGo's Go runtime requires these even for reactor components (empty main())
+/// This is a TinyGo architecture requirement, not a Component Model limitation
 world calculator-world {
+    // TinyGo runtime requires these WASI interfaces
+    import wasi:io/streams@0.2.0;
+    import wasi:cli/stdout@0.2.0;
+    import wasi:cli/stderr@0.2.0;
+    import wasi:cli/stdin@0.2.0;
+    import wasi:clocks/wall-clock@0.2.0;
+    import wasi:filesystem/types@0.2.0;
+    import wasi:filesystem/preopens@0.2.0;
+    import wasi:random/random@0.2.0;
+
     export calculator;
 }

examples/go_component/wit/simple-calculator.wit

@@ -394,18 +394,23 @@ def _compile_tinygo_module(ctx, tinygo, go_binary, wasm_opt_binary, wasm_tools,
 
     # CRITICAL: We DO need WIT flags to tell TinyGo to generate custom WIT exports
     # Without these flags, TinyGo only generates WASI CLI interfaces, not our calculator functions
-    # The issue was with WASI component wrapping, not with WIT export generation
+    # FIX: Use single-dash flags as TinyGo expects: -wit-package and -wit-world (not double-dash)
+    # FIX: Pass the full WIT directory (with deps/) instead of just the file basename
     if ctx.attr.wit and ctx.attr.world:
-        wit_info = ctx.attr.wit[WitInfo]
-        wit_files = wit_info.wit_files.to_list()
-        if wit_files:
-            # TinyGo expects WIT package path and world name for WIT export generation
-            # Since TinyGo executes from the workspace directory, use relative path
-            wit_relative_path = "wit/" + wit_files[0].basename
+        # Get the WIT library directory that contains the full structure with deps/
+        wit_library_dir = None
+        for file in ctx.attr.wit[DefaultInfo].files.to_list():
+            if file.is_directory:
+                wit_library_dir = file
+                break
+
+        if wit_library_dir:
+            # TinyGo expects WIT package directory path for dependency resolution
+            # The wit_library rule creates a directory with proper deps/ structure
             tinygo_args.extend([
-                "--wit-package",
-                wit_relative_path,
-                "--wit-world",
+                "-wit-package",
+                wit_library_dir.path,
+                "-wit-world",
                 ctx.attr.world,
             ])
 
@@ -511,6 +516,11 @@ def _compile_tinygo_module(ctx, tinygo, go_binary, wasm_opt_binary, wasm_tools,
     if ctx.attr.wit:
         wit_info = ctx.attr.wit[WitInfo]
         inputs.extend(wit_info.wit_files.to_list())
+        # Also include the WIT library directory (with deps/) for dependency resolution
+        for file in ctx.attr.wit[DefaultInfo].files.to_list():
+            if file.is_directory:
+                inputs.append(file)
+                break
 
     # CRITICAL FIX: TinyGo needs absolute paths for Go binary
     # Create a wrapper script that sets up the environment with absolute paths
@@ -551,15 +561,26 @@ def _compile_tinygo_module(ctx, tinygo, go_binary, wasm_opt_binary, wasm_tools,
         "",
     ])
 
-    # Add the TinyGo command with arguments, adjusting output path to be absolute
+    # Add the TinyGo command with arguments, adjusting paths to be absolute
     tinygo_cmd = "\"$EXECROOT/{}\"".format(tinygo.path) if not tinygo.path.startswith("/") else "\"{}\"".format(tinygo.path)
 
-    # Adjust the output path to be absolute since we're changing directories
+    # Get the WIT library directory path for adjustment
+    wit_library_path = None
+    if ctx.attr.wit and ctx.attr.world:
+        for file in ctx.attr.wit[DefaultInfo].files.to_list():
+            if file.is_directory:
+                wit_library_path = file.path
+                break
+
+    # Adjust paths to be absolute since we're changing directories
     adjusted_args = []
     for arg in tinygo_args:
         if arg == wasm_module.path:
             # Make output path absolute
             adjusted_args.append("\"$EXECROOT/{}\"".format(wasm_module.path))
+        elif wit_library_path and arg == wit_library_path:
+            # Make WIT package path absolute
+            adjusted_args.append("\"$EXECROOT/{}\"".format(wit_library_path))
         else:
             adjusted_args.append("\"%s\"" % arg)