Pkg-config woes in Heroku build

remeike · March 21, 2024, 3:33am

I’m trying to deploy an application to Heroku that includes webp among its dependencies, and that requires having libwepb, a non-Haskell library, installed on the system as well.

To make this work I’m using two Heroku build packs: heroku-buildpack-webp-binaries to install libwebp and a fork of heroku-buildpack-stack to install stack and build my app.

Their respective build scripts can be found here:

github.com

clhuang/heroku-buildpack-webp-binaries/blob/master/bin/compile

#!/usr/bin/env bash
# bin/compile <build-dir> <cache-dir>

set -e # fail fast

# parse params
BUILD_DIR=$1
CACHE_DIR=$2
BUILDPACK_NAME=webp-binaries

function indent() {
  c='s/^/       /'
  case $(uname) in
    Darwin) sed -l "$c";;
    *)      sed -u "$c";;
  esac
}

function vendor() {
  binary="$1"

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And here:

github.com

mfine/heroku-buildpack-stack/blob/master/bin/compile

#!/usr/bin/env bash
# bin/compile <build-dir> <cache-dir> <env-dir>

set -e
set -o pipefail

# Heroku-provided params
BUILD_DIR="$1"
CACHE_DIR="$2"
ENV_DIR="$3"

function speak (){
  echo "-----> $(date -u '+%Y-%m-%d_%H:%M:%S') $1"
}

speak "Starting..."

BLACKLIST_REGEX="^(PATH|GIT_DIR|CPATH|CPPATH|LD_PRELOAD|LIBRARY_PATH)$"
if [ -d "$ENV_DIR" ]; then
  speak "Exporting config vars"

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However, when I actually try to deploy this application, I get the following error:

webp                             > configure
webp                             > Configuring webp-0.1.0.3...
webp                             > Error: Cabal-simple_6HauvNHV_3.8.1.0_ghc-9.4.7: The pkg-config package
webp                             > 'libwebp' version >=0.6.1 is required but it could not be found.
webp                             > 
Error: [S-7282]

So it can’t find libwebp, however, I believe it is installed in that environment. I even added a webpinfo -version line to the script just to check and it printed: WebP Decoder version: 0.6.1.

Is there something about how pkg-config looks for external dependencies that I should be aware of?

tomjaguarpaw · March 21, 2024, 10:58am

That’s interesting. It seems similar to this issue: Toy GUI project

remeike · March 21, 2024, 4:49pm

This was just foolishness on my part. The problem had nothing to do with the way my Haskell application was built. It was actually in the heroku-buildpack-webp-binaries, which itself worked fine but the package it was installing didn’t have a pkgconfig directory with the necessary .pc file. Although libwebp was installed, when I did pkg-config --modversion libwebp I would get:

Package libwebp was not found in the pkg-config search path.
Perhaps you should add the directory containing `libwebp.pc'
to the PKG_CONFIG_PATH environment variable

So I took a different tack and used APT, via heroku-buildpack-apt, to install the right cocktail of dependencies and it worked. Sorry for the false alarm!