Only use substrate-wasm-builder when std feature is enabled.

bin/node-template/runtime/Cargo.toml

@@ -51,7 +51,7 @@ frame-system-benchmarking = { version = "4.0.0-dev", default-features = false, p
 pallet-template = { version = "4.0.0-dev", default-features = false, path = "../pallets/template" }
 
 [build-dependencies]
-substrate-wasm-builder = { version = "5.0.0-dev", path = "../../../utils/wasm-builder" }
+substrate-wasm-builder = { version = "5.0.0-dev", path = "../../../utils/wasm-builder", optional = true }
 
 [features]
 default = ["std"]
@@ -86,6 +86,7 @@ std = [
 	"sp-std/std",
 	"sp-transaction-pool/std",
 	"sp-version/std",
+	"substrate-wasm-builder",
 ]
 runtime-benchmarks = [
 	"frame-benchmarking/runtime-benchmarks",

bin/node-template/runtime/build.rs

@@ -1,9 +1,10 @@
-use substrate_wasm_builder::WasmBuilder;
-
 fn main() {
-	WasmBuilder::new()
-		.with_current_project()
-		.export_heap_base()
-		.import_memory()
-		.build()
+	#[cfg(feature = "std")]
+	{
+		substrate_wasm_builder::WasmBuilder::new()
+			.with_current_project()
+			.export_heap_base()
+			.import_memory()
+			.build();
+	}
 }

bin/node/runtime/Cargo.toml

@@ -113,7 +113,7 @@ pallet-vesting = { version = "4.0.0-dev", default-features = false, path = "../.
 pallet-whitelist = { version = "4.0.0-dev", default-features = false, path = "../../../frame/whitelist" }
 
 [build-dependencies]
-substrate-wasm-builder = { version = "5.0.0-dev", path = "../../../utils/wasm-builder" }
+substrate-wasm-builder = { version = "5.0.0-dev", path = "../../../utils/wasm-builder", optional = true }
 
 [features]
 default = ["std"]
@@ -205,6 +205,7 @@ std = [
 	"sp-io/std",
 	"pallet-child-bounties/std",
 	"pallet-alliance/std",
+	"substrate-wasm-builder",
 ]
 runtime-benchmarks = [
 	"frame-benchmarking/runtime-benchmarks",

bin/node/runtime/build.rs

@@ -15,12 +15,13 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-use substrate_wasm_builder::WasmBuilder;
-
 fn main() {
-	WasmBuilder::new()
-		.with_current_project()
-		.export_heap_base()
-		.import_memory()
-		.build()
+	#[cfg(feature = "std")]
+	{
+		substrate_wasm_builder::WasmBuilder::new()
+			.with_current_project()
+			.export_heap_base()
+			.import_memory()
+			.build();
+	}
 }

client/executor/runtime-test/Cargo.toml

@@ -19,7 +19,7 @@ sp-runtime = { version = "7.0.0", default-features = false, path = "../../../pri
 sp-std = { version = "5.0.0", default-features = false, path = "../../../primitives/std" }
 
 [build-dependencies]
-substrate-wasm-builder = { version = "5.0.0-dev", path = "../../../utils/wasm-builder" }
+substrate-wasm-builder = { version = "5.0.0-dev", path = "../../../utils/wasm-builder", optional = true }
 
 [features]
 default = ["std"]
@@ -28,4 +28,5 @@ std = [
 	"sp-io/std",
 	"sp-runtime/std",
 	"sp-std/std",
+	"substrate-wasm-builder",
 ]

client/executor/runtime-test/build.rs

@@ -16,22 +16,26 @@
 // You should have received a copy of the GNU General Public License
 // along with this program. If not, see <https://www.gnu.org/licenses/>.
 
-use substrate_wasm_builder::WasmBuilder;
-
 fn main() {
 	// regular build
-	WasmBuilder::new()
-		.with_current_project()
-		.export_heap_base()
-		.import_memory()
-		.build();
+	#[cfg(feature = "std")]
+	{
+		substrate_wasm_builder::WasmBuilder::new()
+			.with_current_project()
+			.export_heap_base()
+			.import_memory()
+			.build();
+	}
 
 	// and building with tracing activated
-	WasmBuilder::new()
-		.with_current_project()
-		.export_heap_base()
-		.import_memory()
-		.set_file_name("wasm_binary_with_tracing.rs")
-		.append_to_rust_flags(r#"--cfg feature="with-tracing""#)
-		.build();
+	#[cfg(feature = "std")]
+	{
+		substrate_wasm_builder::WasmBuilder::new()
+			.with_current_project()
+			.export_heap_base()
+			.import_memory()
+			.set_file_name("wasm_binary_with_tracing.rs")
+			.append_to_rust_flags(r#"--cfg feature="with-tracing""#)
+			.build();
+	}
 }

primitives/runtime-interface/test-wasm-deprecated/Cargo.toml

@@ -19,8 +19,14 @@ sp-runtime-interface = { version = "7.0.0", default-features = false, path = "..
 sp-std = { version = "5.0.0", default-features = false, path = "../../std" }
 
 [build-dependencies]
-substrate-wasm-builder = { version = "5.0.0-dev", path = "../../../utils/wasm-builder" }
+substrate-wasm-builder = { version = "5.0.0-dev", path = "../../../utils/wasm-builder", optional = true }
 
 [features]
 default = [ "std" ]
-std = [ "sp-core/std", "sp-io/std", "sp-runtime-interface/std", "sp-std/std" ]
+std = [
+    "sp-core/std",
+    "sp-io/std",
+    "sp-runtime-interface/std",
+    "sp-std/std",
+    "substrate-wasm-builder",
+]

primitives/runtime-interface/test-wasm-deprecated/build.rs

@@ -15,12 +15,13 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-use substrate_wasm_builder::WasmBuilder;
-
 fn main() {
-	WasmBuilder::new()
-		.with_current_project()
-		.export_heap_base()
-		.import_memory()
-		.build()
+	#[cfg(feature = "std")]
+	{
+		substrate_wasm_builder::WasmBuilder::new()
+			.with_current_project()
+			.export_heap_base()
+			.import_memory()
+			.build();
+	}
 }

primitives/runtime-interface/test-wasm/Cargo.toml

@@ -20,8 +20,14 @@ sp-runtime-interface = { version = "7.0.0", default-features = false, path = "..
 sp-std = { version = "5.0.0", default-features = false, path = "../../std" }
 
 [build-dependencies]
-substrate-wasm-builder = { version = "5.0.0-dev", path = "../../../utils/wasm-builder" }
+substrate-wasm-builder = { version = "5.0.0-dev", path = "../../../utils/wasm-builder", optional = true }
 
 [features]
 default = [ "std" ]
-std = [ "sp-core/std", "sp-io/std", "sp-runtime-interface/std", "sp-std/std" ]
+std = [
+    "sp-core/std",
+    "sp-io/std",
+    "sp-runtime-interface/std",
+    "sp-std/std",
+    "substrate-wasm-builder",
+]

primitives/runtime-interface/test-wasm/build.rs

@@ -15,12 +15,13 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-use substrate_wasm_builder::WasmBuilder;
-
 fn main() {
-	WasmBuilder::new()
-		.with_current_project()
-		.export_heap_base()
-		.import_memory()
-		.build()
+	#[cfg(feature = "std")]
+	{
+		substrate_wasm_builder::WasmBuilder::new()
+			.with_current_project()
+			.export_heap_base()
+			.import_memory()
+			.build();
+	}
 }

test-utils/runtime/Cargo.toml

@@ -59,7 +59,7 @@ substrate-test-runtime-client = { version = "2.0.0", path = "./client" }
 futures = "0.3.21"
 
 [build-dependencies]
-substrate-wasm-builder = { version = "5.0.0-dev", path = "../../utils/wasm-builder" }
+substrate-wasm-builder = { version = "5.0.0-dev", path = "../../utils/wasm-builder", optional = true }
 
 [features]
 default = [
@@ -101,6 +101,7 @@ std = [
 	"sp-trie/std",
 	"sp-transaction-pool/std",
 	"trie-db/std",
+	"substrate-wasm-builder",
 ]
 # Special feature to disable logging
 disable-logging = [ "sp-api/disable-logging" ]

test-utils/runtime/build.rs

@@ -15,24 +15,28 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-use substrate_wasm_builder::WasmBuilder;
-
 fn main() {
-	WasmBuilder::new()
-		.with_current_project()
-		.export_heap_base()
-		// Note that we set the stack-size to 1MB explicitly even though it is set
-		// to this value by default. This is because some of our tests (`restoration_of_globals`)
-		// depend on the stack-size.
-		.append_to_rust_flags("-Clink-arg=-zstack-size=1048576")
-		.import_memory()
-		.build();
+	#[cfg(feature = "std")]
+	{
+		substrate_wasm_builder::WasmBuilder::new()
+			.with_current_project()
+			.export_heap_base()
+			// Note that we set the stack-size to 1MB explicitly even though it is set
+			// to this value by default. This is because some of our tests
+			// (`restoration_of_globals`) depend on the stack-size.
+			.append_to_rust_flags("-Clink-arg=-zstack-size=1048576")
+			.import_memory()
+			.build();
+	}
 
-	WasmBuilder::new()
-		.with_current_project()
-		.export_heap_base()
-		.import_memory()
-		.set_file_name("wasm_binary_logging_disabled.rs")
-		.enable_feature("disable-logging")
-		.build();
+	#[cfg(feature = "std")]
+	{
+		substrate_wasm_builder::WasmBuilder::new()
+			.with_current_project()
+			.export_heap_base()
+			.import_memory()
+			.set_file_name("wasm_binary_logging_disabled.rs")
+			.enable_feature("disable-logging")
+			.build();
+	}
 }

utils/wasm-builder/README.md

@@ -8,23 +8,24 @@ The Wasm builder is a tool that integrates the process of building the WASM bina
 A project that should be compiled as a Wasm binary needs to:
 
 1. Add a `build.rs` file.
-2. Add `wasm-builder` as dependency into `build-dependencies`.
+2. Add `wasm-builder` as dependency into `build-dependencies` (can be made optional and only enabled when `std` feature is used).
 
 The `build.rs` file needs to contain the following code:
 
 ```rust
-use substrate_wasm_builder::WasmBuilder;
-
 fn main() {
-    WasmBuilder::new()
-        // Tell the builder to build the project (crate) this `build.rs` is part of.
-        .with_current_project()
-        // Make sure to export the `heap_base` global, this is required by Substrate
-        .export_heap_base()
-        // Build the Wasm file so that it imports the memory (need to be provided by at instantiation)
-        .import_memory()
-        // Build it.
-        .build()
+    #[cfg(feature = "std")]
+    {
+        substrate_wasm_builder::WasmBuilder::new()
+            // Tell the builder to build the project (crate) this `build.rs` is part of.
+            .with_current_project()
+            // Make sure to export the `heap_base` global, this is required by Substrate
+            .export_heap_base()
+            // Build the Wasm file so that it imports the memory (need to be provided by at instantiation)
+            .import_memory()
+            // Build it.
+            .build();
+    }
 }
 ```