feat: specify the location of the derivation with derivation-path (#5)

- Add `derivation-path` input to specify the location of the `shell.nix`
or `default.nix`.
- Add unit tests and integration tests for this functionality.

Related to #4.

Author: cgrindel

.github/workflows/ci.yaml

@@ -43,10 +43,12 @@ jobs:
       - uses: ./.github/actions/set_up_runner
         with:
           github_token: ${{ secrets.GITHUB_TOKEN }}
-      - name: Execute simple
+      - name: Execute in directory with shell.nix
         uses: ./
         with:
           verbose: true
+          # Demonstrate passing a directory that contains a shell.nix.
+          derivation-path: ./tests/integration_tests
           working-directory: ./tests/integration_tests
           options: |
             --arg customVarBool true
@@ -55,7 +57,7 @@ jobs:
             echo "FIRST" > integration_test.out
             echo "${CUSTOM_VAR_BOOL}" >> integration_test.out
             echo "${CUSTOM_VAR_STR}" >> integration_test.out
-      - name: Confirm output
+      - name: Confirm output for Execute in directory with shell.nix
         shell: bash
         run: |
           output="$(<./tests/integration_tests/integration_test.out)"
@@ -67,6 +69,26 @@ jobs:
           )"
           [[ "${output}" == "${expected}" ]] || \
             (echo >&2 "Ouptput from integration test does not match:" "${output}"; exit 1)
+      - name: Execute in directory without shell.nix
+        uses: ./
+        with:
+          verbose: true
+          # Demonstrate passing a path to a shell.nix.
+          derivation-path: ./tests/integration_tests/shell.nix
+          options: |
+            --argstr customVarStr "Hello, World!"
+          run: |
+            echo "${CUSTOM_VAR_STR}" >> integration_test2.out
+      - name: Confirm output for Execute in directory without shell.nix
+        shell: bash
+        run: |
+          output="$(<./integration_test2.out)"
+          expected="$(cat <<-EOF
+          Hello, World!
+          EOF
+          )"
+          [[ "${output}" == "${expected}" ]] || \
+            (echo >&2 "Ouptput from integration test does not match:" "${output}"; exit 1)
 
   all_ci_tests:
     runs-on: ubuntu-latest

action.yaml

@@ -14,8 +14,14 @@ inputs:
     description: Any parameters that are to be passed to nix-shell are specified here.
   working-directory:
     type: string
-    description: The path where the nix-shell execution should take place.
+    description: |
+      The path where the script will be executed. This is not the path where nix-shell is executed.
     default: .
+  derivation-path:
+    type: string
+    description: |
+      The path to directory or the shell.nix or default.nix to use to set up the environment. This
+      is the directory where nix-shell is executed.
   verbose:
     type: boolean
     description: Enable debug output written to stderr.
@@ -30,5 +36,6 @@ runs:
         RNS_OPTS: ${{ inputs.options }}
         RNS_RUN: ${{ inputs.run }}
         RNS_PURE: ${{ inputs.pure }}
+        RNS_DERIVATION_PATH: ${{ inputs.derivation-path }}
         RNS_VERBOSE: ${{ inputs.verbose }}
       run: ${GITHUB_ACTION_PATH}/tools/run_nix_shell.sh

tests/tools_tests/BUILD.bazel

@@ -4,6 +4,8 @@ run_nix_shell_test(name = "custom_var_bool_test")
 
 run_nix_shell_test(name = "custom_var_str_test")
 
+run_nix_shell_test(name = "derivation_path_test")
+
 run_nix_shell_test(name = "multi_line_script_test")
 
 run_nix_shell_test(name = "pure_test")

tests/tools_tests/derivation_path_test.sh

@@ -0,0 +1,10 @@
+assert_msg="custom derivation path via RNS_DERIVATION_PATH"
+derivation_path="${PWD}/shell.nix"
+another_dir="${PWD}/somewhere_else"
+mkdir -p "${another_dir}"
+output="$( 
+RNS_DERIVATION_PATH="${derivation_path}" \
+  RNS_CWD="${another_dir}" \
+  "${run_nix_shell_sh}" 'echo "${CUSTOM_VAR_STR}"' 
+)"
+assert_match "default" "${output}" "${assert_msg}"

tools/run_nix_shell.sh

@@ -14,10 +14,20 @@ fail() {
   exit 1
 }
 
+absolute_path() {
+  local path="${1}"
+  local bname
+  local dname
+  bname="$( basename "${path}" )"
+  dname="$( dirname "${path}" )"
+  echo "$( cd "${dname}"; pwd )/${bname}"
+}
+
 # MARK - Arguments
 
 cwd="${RNS_CWD:-}"
 script="${RNS_RUN:-}"
+derivation_path="${RNS_DERIVATION_PATH:-}"
 
 pure="${RNS_PURE:-true}"
 verbose="${RNS_VERBOSE:-false}"
@@ -70,11 +80,13 @@ if is_verbose; then
 RNS_CWD: ${RNS_CWD:-}
 RNS_OPTS: ${RNS_OPTS:-}
 RNS_RUN: ${RNS_RUN:-}
+RNS_DERIVATION_PATH: ${RNS_DERIVATION_PATH:-}
 RNS_PURE: ${RNS_PURE:-}
 cwd: ${cwd:-}
 nix_shell_opts: $( printf "%q " "${nix_shell_opts[@]}" )
 pure: ${pure:-}
 script: ${script:-}
+derivation_path: ${derivation_path:-}
 ===
 EOF
 )"
@@ -83,6 +95,30 @@ fi
 
 # MARK - Process Options and Arguments
 
+# Resolve the target directory to an absolute path before processing the
+# derivation path. That logic may change directories.
+if [[ -n "${cwd:-}" ]]; then
+  cwd="$( absolute_path "${cwd}" )"
+fi
+
+# The shell.nix or default.nix may contain relative paths to other files. The
+# Nix logic does not appear to resolve these relative to the file, but to the
+# current directory. So, we will ensure that we are in the derivation's
+# directory before executing the command.
+if [[ -n "${derivation_path:-}" ]]; then
+  derivation_path="$( absolute_path "${derivation_path}" )"
+  if [[ -d "${derivation_path}" ]]; then
+    derivation_dirname="${derivation_path}"
+  else
+    derivation_dirname="$( dirname "${derivation_path}" )"
+    derivation_basename="$( basename "${derivation_path}" )"
+  fi
+  cd "${derivation_dirname}"
+  if [[ -n "${derivation_basename:-}" ]]; then
+    nix_shell_opts+=( "${derivation_basename}" )
+  fi
+fi
+
 if [[ "${pure}" == "true" ]]; then
   nix_shell_opts+=( --pure )
 fi
@@ -101,16 +137,22 @@ if [[ -n "${RNS_OPTS:-}" ]]; then
 fi
 
 if [[ -z "${script:-}" ]]; then
-  fail "A script for a path to a file must be provided."
+  fail "A script or a path to a file must be provided."
 fi
 
 # MARK - Execute script
 
 # Change to the specified working directory
 if [[ -n "${cwd:-}" ]]; then
-  cd "${cwd}"
+  cd_cmd="cd ${cwd}"
 fi
 
+script="$(cat <<-EOF
+${cd_cmd:-}
+${script}
+EOF
+)"
+
 cmd=( nix-shell )
 if [[ ${#nix_shell_opts[@]} -gt 0 ]]; then
   cmd+=( "${nix_shell_opts[@]}" )
@@ -120,6 +162,7 @@ cmd+=( --run "${script}" )
 if is_verbose; then
   verbose_output="$(cat <<-EOF
 === run_nix_shell command-line invocation ===
+pwd: ${PWD}
 $( printf "%q " "${cmd[@]}" )
 ===
 EOF