to-stderr

README.md

@@ -15,6 +15,7 @@ A collection of utility components that remix wasi:logging types and interfaces.
 ## Components
 
 - [`levels`](./components/levels/)
+- [`to-stderr`](./components/to-stderr/)
 - [`to-stdout`](./components/to-stdout/)
 
 ## Build
@@ -31,7 +32,7 @@ make components
 
 The build creates each component in [`components`](./components) into `target/components`, e.g. the levels component at `target/components/levels/levels.wasm`, along with `target/components/interface.wasm`, the `componentized:logging` WIT package. Each component is also built with debug info, e.g. `target/components/levels/levels.debug.wasm`.
 
-The cli tools the build uses, [`wasm-tools`](https://github.com/bytecodealliance/wasm-tools) and [`wkg`](https://github.com/bytecodealliance/wasm-pkg-tools), are pinned in [`tools/Cargo.toml`](./tools/Cargo.toml) and installed into `target/tools/<platform>`, e.g. `target/tools/aarch64-apple-darwin`, as needed, or ahead of time with `make tools`. Dependabot bumps the pinned versions.
+The cli tools the build uses, [`wac`](https://github.com/bytecodealliance/wac), [`wasm-tools`](https://github.com/bytecodealliance/wasm-tools) and [`wkg`](https://github.com/bytecodealliance/wasm-pkg-tools), are pinned in [`tools/Cargo.toml`](./tools/Cargo.toml) and installed into `target/tools/<platform>`, e.g. `target/tools/aarch64-apple-darwin`, as needed, or ahead of time with `make tools`. Dependabot bumps the pinned versions.
 
 ## Community
 

components/to-stderr/README.md

@@ -0,0 +1,9 @@
+# `to-stderr`
+
+Implements wasi:logging/logging@0.1.0-draft writing log statements to stderr via wasi:cli/stderr@0.3.0. A composition of [`to-stdout`](../to-stdout/) with its wasi:cli/stdout@0.3.0 import satisfied by wasi:cli/stderr@0.3.0.
+
+Log output takes the form:
+
+```
+2025-02-10 18:04:35.925Z LEVEL [component]: message
+```

components/to-stderr/to-stderr.wac

@@ -0,0 +1,11 @@
+package componentized:logging;
+
+import stderr: wasi:cli/stderr@0.3.0;
+
+let to-stdout = new local:to-stdout {
+    // write log statements to stderr instead of stdout
+    "wasi:cli/stdout@0.3.0": stderr,
+    ...
+};
+
+export to-stdout["wasi:logging/logging@0.1.0-draft"];

make/components.mk

@@ -1,10 +1,14 @@
 COMPONENTS_DIR := target/components
 
+# the WIT packages of components/wit/deps, encoded where `wac compose` looks for a package a
+# composition names without instantiating it, e.g. `import stderr: wasi:cli/stderr@0.3.0;`
+WAC_DEPS_DIR := target/wac-deps
+
 COMPONENTS = $(sort $(foreach file,$(wildcard $(addprefix components/*/,wit/*.constants.wit *.properties *.wac *.wkg Cargo.toml)),$(word 2,$(subst /, ,$(file)))))
 
 .PHONY: clean-components
 clean-components: clean-wit
-	rm -rf ${COMPONENTS_DIR}
+	rm -rf ${COMPONENTS_DIR} ${WAC_DEPS_DIR}
 
 .PHONY: components
 components: ${COMPONENTS_DIR}/interface.wasm $(foreach component,$(COMPONENTS),${COMPONENTS_DIR}/$(component)/$(component).wasm ${COMPONENTS_DIR}/$(component)/$(component).debug.wasm)
@@ -35,11 +39,11 @@ else ifneq ($(wildcard components/$1/$1.wac),)
 # the local packages the composition instantiates, e.g. `new local:latch-n2 { ... }`
 WAC_DEPS_$1 := $$(shell grep -v '^\s*//' components/$1/$1.wac | grep -oE 'local:[a-z0-9-]+' | sed 's/^local://' | sort -u)
 
-${COMPONENTS_DIR}/$1/$1.wasm: components/$1/$1.wac $$(foreach component,$$(WAC_DEPS_$1),$${COMPONENTS_DIR}/$$(component)/$$(component).wasm) ${COMPONENTS_DIR}/$1/README.md | $(call tool,wac-cli)
-	$(WAC) compose $$(foreach component,$$(WAC_DEPS_$1),-d local:$$(component)=$${COMPONENTS_DIR}/$$(component)/$$(component).wasm) -o ${COMPONENTS_DIR}/$1/$1.wasm components/$1/$1.wac
+${COMPONENTS_DIR}/$1/$1.wasm: components/$1/$1.wac $$(foreach component,$$(WAC_DEPS_$1),$${COMPONENTS_DIR}/$$(component)/$$(component).wasm) ${COMPONENTS_DIR}/$1/README.md ${WAC_DEPS_DIR} | $(call tool,wac-cli)
+	$(WAC) compose --deps-dir ${WAC_DEPS_DIR} $$(foreach component,$$(WAC_DEPS_$1),-d local:$$(component)=$${COMPONENTS_DIR}/$$(component)/$$(component).wasm) -o ${COMPONENTS_DIR}/$1/$1.wasm components/$1/$1.wac
 
-${COMPONENTS_DIR}/$1/$1.debug.wasm: components/$1/$1.wac $$(foreach component,$$(WAC_DEPS_$1),$${COMPONENTS_DIR}/$$(component)/$$(component).debug.wasm) ${COMPONENTS_DIR}/$1/README.md | $(call tool,wac-cli)
-	$(WAC) compose $$(foreach component,$$(WAC_DEPS_$1),-d local:$$(component)=$${COMPONENTS_DIR}/$$(component)/$$(component).debug.wasm) -o ${COMPONENTS_DIR}/$1/$1.debug.wasm components/$1/$1.wac
+${COMPONENTS_DIR}/$1/$1.debug.wasm: components/$1/$1.wac $$(foreach component,$$(WAC_DEPS_$1),$${COMPONENTS_DIR}/$$(component)/$$(component).debug.wasm) ${COMPONENTS_DIR}/$1/README.md ${WAC_DEPS_DIR} | $(call tool,wac-cli)
+	$(WAC) compose --deps-dir ${WAC_DEPS_DIR} $$(foreach component,$$(WAC_DEPS_$1),-d local:$$(component)=$${COMPONENTS_DIR}/$$(component)/$$(component).debug.wasm) -o ${COMPONENTS_DIR}/$1/$1.debug.wasm components/$1/$1.wac
 
 else ifneq ($(wildcard components/$1/$1.wkg),)
 
@@ -70,6 +74,9 @@ endef
 
 $(foreach component,$(COMPONENTS),$(eval $(call BUILD_COMPONENT,$(component))))
 
+${WAC_DEPS_DIR}: components/wit/deps scripts/wac-deps.sh | $(call tool,wasm-tools)
+	WASM_TOOLS=$(WASM_TOOLS) scripts/wac-deps.sh components/wit/deps ${WAC_DEPS_DIR}
+
 ${COMPONENTS_DIR}/interface.wasm: wit/deps README.md | $(call tool,wkg)
 	@mkdir -p ${COMPONENTS_DIR}
 	$(WKG) build -o ${COMPONENTS_DIR}/interface.wasm

scripts/wac-deps.sh

@@ -0,0 +1,46 @@
+#!/usr/bin/env bash
+
+# Encode each WIT package of a wit/deps directory where `wac compose --deps-dir` looks for it, so a
+# composition can name the interfaces of a package it does not instantiate, e.g.
+# `import stderr: wasi:cli/stderr@0.3.0;`.
+#
+#   WASM_TOOLS=<wasm-tools> scripts/wac-deps.sh <wit/deps> <deps-dir>
+#
+# wac looks for a versioned package at `<namespace>/<name>/<version>.wasm`, e.g.
+#
+#   wit/deps/wasi-cli-0.3.0  -> <deps-dir>/wasi/cli/0.3.0.wasm
+#
+# Each package is encoded with the other packages as its dependencies.
+
+set -euo pipefail
+
+deps=$1
+out=$2
+wasm_tools=${WASM_TOOLS:-wasm-tools}
+
+work=$(mktemp -d)
+trap 'rm -rf "$work"' EXIT
+
+rm -rf "$out"
+mkdir -p "$out"
+
+for package in "$deps"/*/; do
+  package=${package%/}
+  rm -rf "$work/package"
+  mkdir -p "$work/package/deps"
+  cp "$package"/*.wit "$work/package/"
+  for dep in "$deps"/*/; do
+    dep=${dep%/}
+    [[ "$dep" == "$package" ]] || cp -R "$dep" "$work/package/deps/"
+  done
+  "$wasm_tools" component wit "$work/package" --wasm -o "$work/package.wasm"
+
+  # e.g. `package wasi:cli@0.3.0;`
+  id=$("$wasm_tools" component wit "$work/package.wasm" | sed -n 's/^package \(.*\);$/\1/p' | head -n 1)
+  namespace=${id%%:*}
+  name=${id#*:}
+  name=${name%%@*}
+  version=${id#*@}
+  mkdir -p "$out/$namespace/$name"
+  cp "$work/package.wasm" "$out/$namespace/$name/$version.wasm"
+done

tools/Cargo.toml

@@ -15,10 +15,12 @@ path = "lib.rs"
 # the binaries each tool installs, the Makefile runs each by path from a variable named after it,
 # e.g. `$(WASM_TOOLS)` for `wasm-tools`
 [package.metadata.bins]
+wac-cli = ["wac"]
 wasm-tools = ["wasm-tools"]
 wkg = ["wkg"]
 
 [dependencies]
+wac-cli = "=0.12.0"
 wasm-tools = "=1.261.0"
 wkg = "=0.16.1"