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First build fails due to missing inputs created by repository_rule

See original GitHub issue

The first build fails, but immediately building again succeeds. The setup is unusual: npm installation creates a directory in the user’s project, which we want to use as inputs to later actions.

Repro:

WORKSPACE

workspace(name = "repro")
load("//:defs.bzl", "repo")
repo(file_in_project = "//:BUILD")

defs.bzl

def _repo_rule_impl(ctx):
  # Grab a reference to the root of the users project
  project_dir = ctx.path(ctx.attr.file_in_project).dirname
  # Emulate installing npm dependencies there
  ctx.file("install.sh", """#!/bin/bash
  cd $(dirname $1)
  mkdir node_modules
  echo "hello" > node_modules/some-file.txt
  ls -R
  """)
  result = ctx.execute(["./install.sh", ctx.path(ctx.attr.file_in_project)])
  print(result.stdout)
  if result.return_code > 0:
    print(result.stderr)
  # Create a symlink so external repo can reference the installed node packages
  ctx.symlink(project_dir, "installed")

_repo_rule = repository_rule(_repo_rule_impl,
  attrs = {"file_in_project": attr.label()})

def repo(file_in_project):
  _repo_rule(name = "foo", file_in_project=file_in_project)

BUILD

filegroup(
    name = "generated",
    srcs=glob(["node_modules/**"]),
    visibility=["//visibility:public"]
)

genrule(
  name = "test",
  outs = ["out"],
  cmd = "echo works > $@",
  # This points through the symlink to the filegroup above
  srcs = ["@foo//installed:generated"]
)

On the initial build (or after rm -rf node_modules/; bazel clean --expunge) the build fails. Note that the node_modules directory doesn’t exist in the project at the start of the build, but does exist before the actions execute:

$ bazel build :test
...........
WARNING: /home/alexeagle/repro6/defs.bzl:13:3: .:
BUILD
defs.bzl
node_modules
WORKSPACE

./node_modules:
some-file.txt
.
INFO: Found 1 target...
ERROR: missing input file '@foo//installed:node_modules/some-file.txt'.
ERROR: /home/alexeagle/repro6/BUILD:2:1: //:test: missing input file '@foo//installed:node_modules/some-file.txt'.
Target //:test failed to build
Use --verbose_failures to see the command lines of failed build steps.
ERROR: /home/alexeagle/repro6/BUILD:2:1 1 input file(s) do not exist.
INFO: Elapsed time: 2.505s, Critical Path: 0.01s

Now the node_modules directory exists before the build starts, and simply building again succeeds:

$ bazel build :test
WARNING: /home/alexeagle/repro6/defs.bzl:12:3: .:
BUILD
defs.bzl
node_modules
WORKSPACE

./node_modules:
some-file.txt
.
INFO: Found 1 target...
Target //:test up-to-date:
  bazel-genfiles/out
INFO: Elapsed time: 0.213s, Critical Path: 0.00s