Update package.json version in Bazel rule - package.json

Question

I'm trying to create a Bazel rule that will update the version number in package.json before packing with npm_package.
In short I want to take packages/server/package.tpl.json and create an output package.json that I can depend on in npm_package.
I've tried a bunch of different was that include error such as read-only file system, no such attribute 'out' in 'stamp_package_json' rule and rule 'package_json' has file 'package.json' as both an input and an output and the current error The following files have no generating action: packages/server/package.json
My project structure looks like:
/
/packages
/server
/src
BUILD.blaze
BUILD.blaze
package.tpl.json
/tools
/npm
BUILD.blaze
stamp_package_json.bzl
This is a monorepo so it has more packages then just server.
In packages/server/BUILD.blaze I use two rules:
package(default_visibility=["//visibility:public"])
load("#build_bazel_rules_nodejs//:defs.bzl", "npm_package")
load("//tools/npm:stamp_package_json.bzl", "stamp_package_json")
stamp_package_json(
name = "package_json",
package_json = "package.tpl.json",
out = "package.json"
)
npm_package(
name = "red-server_package",
deps = [
":package_json",
"//packages/server/src:shared-red-server-library"
],
replacements = {"//packages/": "//"},
)
If I rename package.tpl.json to package.json and just include that file in npm_package it works as expected, except that the version is incorrect.
The stamp_package_json rule is defined in tools/npm/stamp_package_json.bzl:
def _impl(ctx):
package_json = ctx.file.package_json
# The command may only access files declared in inputs.
ctx.actions.run_shell(
inputs = [package_json],
outputs = [ctx.outputs.executable],
arguments=[package_json.path],
progress_message = "Stamping package.json file %s" % package_json.short_path,
command="jq '.version=\"123\"' $1 > $#")
stamp_package_json = rule(
implementation=_impl,
executable = True,
attrs = {
"package_json" : attr.label(allow_single_file=True),
"out": attr.output(mandatory = True)
}
)
As mentioned above it currently throws an error:
The following files have no generating action: packages/server/package.json
I can't seem to figure out how to deal with this. Or if my approach is any good. Or if this can be achieved in any other way.
edit: Wrote a blog post about the solution I ended up with: https://medium.com/red-flag/developer-diary-day-1-bazel-build-system-with-monorepo-and-typescript-6f7a5a0a2b00

Answer 1

Looking into the blog post mentioned in the question, the work of transforming package.tpl.json to package.json can be done with a genrule
genrule(
name = "package_json",
srcs = ["package.tpl.json"],
outs = ["package.json"],
cmd = "jq --arg version $$(cat $(GENDIR)/../../volatile-status.txt | sed -nE 's/^BUILD_SCM_VERSION v([0-9.]+).*$$/\\1/p') '.version=$$version' <$< > $#",
stamp = True
)
npm_package(
name = "shared-red-server-library_package",
deps = [
":package_json",
":shared-red-server-library"
],
replacements = {"//shared_red_node_library/packages/server/": "//"},
)
This looks like a good solution, except it brings external dependency on unix tools jq and sed, so build fails if either is missing or if the environment has some weird incompatible version of it.