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Conditionally skipping post-build scripts in Unity Build Automation when builds fail

Updated

This article explains why Unity Build Automation (UBA) post-build scripts run even when a build fails and how to prevent uploading empty build artifacts in such cases. UBA always executes post-build scripts after the Unity Editor finishes in the builder, regardless of build success. There is no direct “build success” flag, but UBA exposes UNITY_PLAYER_PATH, which only exists on successful builds. By checking that path’s existence at the start of the post-build script, you can safely skip zipping and uploading when builds fail.

 

Symptoms

  • Your post-build script runs even when the UBA build fails.
  • An empty build ZIP is uploaded after a failed build.
  • There is no obvious environment variable indicating whether the Player or an Addressables build succeeded.
  • There is a desire to avoid iterating through directories to verify output files.

Cause

Unity Build Automation is designed to always execute a configured post-build script after the Unity Editor process terminates, just before artifact upload. It does not provide a built-in configuration or a boolean environment variable (such as BUILD_SUCCESS) to conditionally skip the post-build script based on build success or failure. As a result, the post-build script runs unconditionally, which can lead to zipping and uploading empty or missing build artifacts when a build fails.

Resolution

  1. Keep using the post-build script, but add an early existence check for the build artifact.
  2. Use the UNITY_PLAYER_PATH environment variable, which points to the expected Player build output on success.
  3. At the top of your post-build script, resolve UNITY_PLAYER_PATH and verify that the file or directory exists.
  4. If UNITY_PLAYER_PATH does not exist, exit the script before zipping or uploading artifacts.

  5. Below is an example post-build bash script:

    #!/bin/bash

# 1. Grab the artifact path
PLAYER_PATH="$UNITY_PLAYER_PATH"

# 2. Convert Cygwin path to Windows format if using a Windows builder
if [[ "$BUILDER_OS" == "WINDOWS" ]]; then
  PLAYER_PATH=$(cygpath -wa "$UNITY_PLAYER_PATH")
fi

# 3. Check if the artifact actually exists
if [ ! -e "$PLAYER_PATH" ]; then
  echo "Build artifact not found at $PLAYER_PATH. The build likely failed."
  echo "Skipping zip and upload process."
  exit 0  # or exit 1 if you want the job to fail explicitly
fi

# 4. (Optional) Add similar checks for Addressables output paths
# if [ ! -e "path/to/addressables/output" ]; then
#   echo "Addressables output not found. Skipping related steps."
#   exit 0
# fi

echo "Build artifacts found! Proceeding with zipping and uploading..."
# Execute your zipping/uploading logic here
  6. For Addressables (as shown above), add analogous checks for the known output directory or files.

This approach avoids directory-wide scanning and prevents uploading empty ZIPs when the build or Addressables step fails.

More Information

For more information about environment variables, please review this documentation section.

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