Building .NET Core App on circleci with caching packages. Restore only if required.

.circleci-dotnet-with-cache.yml

#
# The fallowing circleci config yml and bash scripts demonstrate 
# how to build .NET Core app without restoring packages for every build 
# until you referance smothing diffrent to any project inside sln.
#
# If you are building docker container when building your application,
# use the docker layer caching insted of these scripts. https://circleci.com/docs/2.0/docker-layer-caching/
#

version: 2

jobs:
  build:
    docker:
      - image: microsoft/dotnet:2.1.500-sdk
    
    steps:
      - checkout

      - run:
          name: Dotnet Packages Checksum File
          command: bash ./ci-dotnet-packages.sh

      - restore_cache:
          keys:
            - dotnet-packages-key-v1-{{ checksum "packages.txt" }}
      - run: 
          name: Restore Packages
          command: bash ./ci-dotnet-restore.sh
      - save_cache:
          key: dotnet-packages-key-v1-{{ checksum "packages.txt" }}
          paths:
            - ~/.nuget/packages
            - ./objs.tar.gz

      - run:
          name: Build
          command: bash ./ci-build.sh

# Now, you can zip your packages and deploy to somewhere.

ci-build.sh

#!/bin/bash
set -euo pipefail
IFS=$'\n\t'

PROJECT_NAME="./src/Example.Web" # change the project name.

# build projects.
dotnet build --no-restore -c Release

# publish artifacts to root folder. 
# You can call only the pulish without --no-build option, if you are not building something not referanced on your project.
dotnet publish $PROJECT_NAME.csproj --no-build --no-restore -c Release -o ../artifacts

ci-dotnet-packages.sh

#!/bin/bash
#
# Find recursively all the .csproj files on given path
# and extract the package referance lines to packages.txt file.
#
set -euo pipefail
IFS=$'\n\t'

PATHS_TO_FIND="./**/*.csproj" # change it by depend on your project folder structure.

addPackages () {
    local search="$1"

    for path in $search; do
        while read -r line; do
            if [[ $line =~ "<PackageReference" ]]; then
                echo "${line// /}" >> packages.txt
            fi  
        done < "$path"
    done
}

# projects
addPackages $PATHS_TO_FIND

ci-dotnet-restore.sh

#!/bin/bash
#
# .NET Core try to find obj folders to ensure the package required is installed before or not.
# The script collect all the obj folder to zip(tar.gz) file to extract it for the next build.
#
set -euo pipefail
IFS=$'\n\t'

PATHS_TO_FIND="./**/*.csproj" # change it by depend on your project folder structure.

copyObjFolders () {
    local search="$1"

    for path in $search; do
        mkdir -p ./objs/$path/..
        cp -r $path ./objs/$path/..
    done
}

if [ ! -f ./objs.tar.gz ]; then
    #restore
    dotnet restore
    
    #projects
    copyObjFolders $PATHS_TO_FIND

    #zip.
    tar -czf objs.tar.gz -C objs .
else
    #unzip objs
    tar -xzf objs.tar.gz

    echo "Restore skipped."
fi