#18941 `export-codegen` is not resilient to existing contents in `dist/codegen` Issue created by huonw Describe the bug When running

pants export-codegen ...

when there's existing entries in overlapping locations in

dist/

, it doesn't clear out those entries, which can lead to problems: 1. if the existing entries are of a different type (e.g. a file in

dist/

, and writing a directory, or vice versa), running

export-codegen

throws errors like

IntrinsicError: Error opening file .../dist/codegen/entry for writing: Os { code: 21, kind: IsADirectory, message: "Is a directory" }

2. if there's generated directories that have stale contents, they're not removed 3. (if there's symlinks, overwriting the symlinks with the same symlinks failed. This was worked-around in #18809 / #18873, but potentially that work-around could be removed.) Reproducer:

cd $(mktemp -d)

cat > pants.toml <<EOF
[GLOBAL]
pants_version = "2.16.0rc1"
backend_packages = ["pants.backend.shell"]

[anonymous-telemetry]
enabled = false
EOF

cat > BUILD <<EOF
shell_command(
  name="directory",
  command="mkdir -p entry; touch entry/new_file.txt",
  tools=["mkdir", "touch"],
  output_directories=["entry"],
)
shell_command(
  name="file",
  command="touch entry",
  tools=["touch"],
  output_files=["entry"]
)
EOF

pants version

# simulate having done a previous export that had different files:
mkdir -p dist/codegen/entry/existing_file.txt

# BUG 2: existing_file.txt still exists
pants export-codegen :directory
ls dist/codegen/entry
#> existing_file.txt new_file.txt

# BUG 1: errors if `dist/codegen/entry` already exists of a different kind
pants export-codegen :file
#> IntrinsicError: Error opening file .../dist/codegen/entry for writing: Os { code: 21, kind: IsADirectory, message: "Is a directory" }

Pants version 2.16.0rc1, but likely affects all versions OS macOS Additional info This is the equivalent of #17758 and #18849 for

export-codegen

instead of

package

. #18930 built infrastructure with

write_digest(..., clear_paths=...)

that makes fixing this easier. pantsbuild/pants