tests: add some transitions for wasi/wasm targets

tests/extra_targets/wasm/transitions.bzl

@@ -0,0 +1,83 @@
+"""Some alias rules that transition `--platforms`."""
+
+def _wasm_platform_transition(_settings, _attr):
+    return {
+        "//command_line_option:platforms":
+            str(Label("//tests/extra_targets/wasm:wasm")),
+    }
+
+wasm_platform_transition = transition(
+    implementation = _wasm_platform_transition,
+    inputs = [],
+    outputs = ["//command_line_option:platforms"],
+)
+
+def _wasm_file_impl(ctx):
+    wasm_file = ctx.attr.name
+    wasm_file = ctx.actions.declare_file(wasm_file)
+    ctx.actions.symlink(
+        output = wasm_file,
+        target_file = ctx.executable.src,
+        is_executable = True,
+    )
+
+    return [DefaultInfo(files = depset([wasm_file]))]
+
+wasm_file = rule(
+    implementation = _wasm_file_impl,
+    attrs = {
+        "src": attr.label(
+            executable = True,
+            cfg = wasm_platform_transition,
+            mandatory = True,
+            doc = "TODO",
+        ),
+        "_allowlist_function_transition": attr.label(
+            default = "@bazel_tools//tools/allowlists/function_transition_allowlist"
+        ),
+    },
+    incompatible_use_toolchain_transition = True,
+    doc = "TODO",
+)
+
+###############################################################################
+
+def _wasi_platform_transition(_settings, _attr):
+    return {
+        "//command_line_option:platforms":
+            str(Label("//tests/extra_targets/wasm:wasi")),
+    }
+
+wasi_platform_transition = transition(
+    implementation = _wasi_platform_transition,
+    inputs = [],
+    outputs = ["//command_line_option:platforms"],
+)
+
+def _wasi_file_impl(ctx):
+    wasi_file = ctx.attr.name
+    wasi_file = ctx.actions.declare_file(wasi_file)
+    ctx.actions.symlink(
+        output = wasi_file,
+        target_file = ctx.executable.src,
+        is_executable = True,
+    )
+
+    return [DefaultInfo(files = depset([wasi_file]))]
+
+wasi_file = rule(
+    implementation = _wasi_file_impl,
+    attrs = {
+        "src": attr.label(
+            executable = True,
+            cfg = wasi_platform_transition,
+            mandatory = True,
+            doc = "TODO",
+        ),
+        "_allowlist_function_transition": attr.label(
+            default = "@bazel_tools//tools/allowlists/function_transition_allowlist"
+        ),
+    },
+    incompatible_use_toolchain_transition = True,
+    doc = "TODO",
+)