SERVER-57047 Remove requirement to specify workdir when subprocess.exec'ing shell scripts

5 files changed, 39 insertions, 184 deletions

diff --git a/etc/evergreen.yml b/etc/evergreen.yml
index 1bf79e297b9..ed82ce59cd8 100644
--- a/etc/evergreen.yml
+++ b/etc/evergreen.yml
@@ -383,8 +383,6 @@ functions:
         binary: bash
         args:
           - "src/evergreen/functions/files_remove.sh"
-        env:
-          workdir: ${workdir}
 
   "configure evergreen api credentials": &configure_evergreen_api_credentials
     command: subprocess.exec
@@ -393,8 +391,6 @@ functions:
       binary: bash
       args:
         - "src/evergreen/functions/evergreen_api_credentials_configure.sh"
-      env:
-        workdir: ${workdir}
 
   "configure selected tests credentials": &configure_selected_tests_credentials
     command: subprocess.exec
@@ -405,12 +401,10 @@ functions:
       args:
         - "src/evergreen/functions/selected_tests_credentials_configure.sh"
       env:
-        workdir: ${workdir}
         project: ${project}
         selected_tests_auth_user: ${selected_tests_auth_user}
         selected_tests_auth_token: ${selected_tests_auth_token}
 
-
   "git get project": &git_get_project
     - command: git.get_project
       params:
@@ -471,8 +465,6 @@ functions:
       binary: bash
       args:
         - "src/evergreen/functions/binaries_extract.sh"
-      env:
-        workdir: ${workdir}
 
   "check binary version": &check_binary_version
     command: subprocess.exec
@@ -480,8 +472,6 @@ functions:
       binary: bash
       args:
         - "src/evergreen/functions/binary_version_check.sh"
-      env:
-        workdir: ${workdir}
 
   "fetch benchmarks": &fetch_benchmarks
     command: s3.get
@@ -570,8 +560,6 @@ functions:
       binary: bash
       args:
         - "./src/evergreen/functions/system_resource_info_collect.sh"
-      env:
-        workdir: ${workdir}
 
   # Run a monitor process as a background, system task to periodically
   # display how many threads interesting processes are using.
@@ -583,8 +571,6 @@ functions:
       binary: bash
       args:
         - "./src/evergreen/functions/process_threads_monitor.sh"
-      env:
-        workdir: ${workdir}
 
   "set up credentials": &set_up_credentials
     command: subprocess.exec
@@ -593,8 +579,6 @@ functions:
       silent: true
       args:
         - "./src/evergreen/functions/credentials_setup.sh"
-      env:
-        workdir: ${workdir}
 
   "set up win mount script":
     - *f_expansions_write
@@ -604,8 +588,6 @@ functions:
         silent: true
         args:
           - "./src/evergreen/functions/win_mount_script_setup.sh"
-        env:
-          workdir: ${workdir}
 
   "set up notary client credentials":
     - *f_expansions_write
@@ -615,8 +597,6 @@ functions:
         silent: true
         args:
           - "./src/evergreen/functions/notary_client_credentials_setup.sh"
-        env:
-          workdir: ${workdir}
 
   "f_remote_credentials_setup_exec": &set_up_remote_credentials
     command: subprocess.exec
@@ -625,7 +605,6 @@ functions:
       args:
         - "./src/evergreen/functions/remote_credentials_setup.sh"
       env:
-        workdir: ${workdir}
         private_key_remote_bash_var: ${private_key_remote}
 
   "set up remote credentials":
@@ -640,8 +619,6 @@ functions:
         silent: true
         args:
           - "./src/evergreen/functions/bf_suggestion_service_call.sh"
-        env:
-          workdir: ${workdir}
 
   "upload debugsymbols": &upload_debugsymbols
     command: s3.put
@@ -670,8 +647,6 @@ functions:
         binary: bash
         args:
           - "./src/evergreen/functions/wiredtiger_develop_use.sh"
-        env:
-          workdir: ${workdir}
 
   "shared scons cache pruning":
     - *f_expansions_write
@@ -681,8 +656,6 @@ functions:
         binary: bash
         args:
           - "./src/evergreen/functions/shared_scons_cache_pruning.sh"
-        env:
-          workdir: ${workdir}
 
   "umount shared scons directory":
     - *f_expansions_write
@@ -691,8 +664,6 @@ functions:
         binary: bash
         args:
           - "./src/evergreen/functions/shared_scons_directory_umount.sh"
-        env:
-          workdir: ${workdir}
 
   "get all modified patch files":
     - *f_expansions_write
@@ -701,8 +672,6 @@ functions:
         binary: bash
         args:
           - "./src/evergreen/functions/modified_patch_files_get_all.sh"
-        env:
-          workdir: ${workdir}
 
   # This function should only be called from patch-build-only tasks.
   "get added and modified patch files":
@@ -712,8 +681,6 @@ functions:
         binary: bash
         args:
           - "./src/evergreen/functions/added_and_modified_patch_files_get.sh"
-        env:
-          workdir: ${workdir}
 
   "determine resmoke jobs": &determine_resmoke_jobs
     command: subprocess.exec
@@ -721,8 +688,6 @@ functions:
       binary: bash
       args:
         - "./src/evergreen/functions/resmoke_jobs_determine.sh"
-      env:
-        workdir: ${workdir}
 
   "update resmoke jobs expansions": &update_resmoke_jobs_expansions
     command: expansions.update
@@ -736,8 +701,6 @@ functions:
       binary: bash
       args:
         - "./src/evergreen/functions/task_timeout_determine.sh"
-      env:
-        workdir: ${workdir}
 
   "update task timeout expansions": &update_task_timeout_expansions
     command: expansions.update
@@ -786,8 +749,8 @@ functions:
       args:
         - "src/evergreen/functions/venv_setup.sh"
       env:
-        workdir: ${workdir}
         pip_dir: ${pip_dir}
+        workdir: ${workdir}
 
   "upload pip requirements": &upload_pip_requirements
     command: s3.put
@@ -852,8 +815,6 @@ functions:
       binary: bash
       args:
         - "./src/evergreen/multiversion_setup.sh"
-      env:
-        workdir: ${workdir}
 
   "do multiversion setup":
     - *f_expansions_write
@@ -866,8 +827,6 @@ functions:
       binary: bash
       args:
         - "./src/evergreen/compiled_binaries_get.sh"
-      env:
-        workdir: ${workdir}
 
   "generate powercycle tasks":
     - *f_expansions_write
@@ -879,8 +838,6 @@ functions:
         binary: bash
         args:
           - "./src/evergreen/powercycle_tasks_generate.sh"
-        env:
-          workdir: ${workdir}
 
     - command: archive.targz_pack
       params:
@@ -917,8 +874,6 @@ functions:
         binary: bash
         args:
           - "./src/evergreen/powercycle_sentinel_run.sh"
-        env:
-          workdir: ${workdir}
 
   "execute resmoke tests": &execute_resmoke_tests
     command: subprocess.exec
@@ -927,8 +882,6 @@ functions:
       binary: bash
       args:
         - "./src/evergreen/resmoke_tests_execute.sh"
-      env:
-        workdir: ${workdir}
 
   "retrieve generated test configuration": &retrieve_generated_test_configuration
     command: s3.get
@@ -960,8 +913,6 @@ functions:
         binary: bash
         args:
           - "./src/evergreen/selected_tests_generate.sh"
-        env:
-          workdir: ${workdir}
     - command: archive.targz_pack
       params:
         target: generate_tasks_config.tgz
@@ -994,8 +945,6 @@ functions:
         binary: bash
         args:
           - "./src/evergreen/burn_in_tests_generate.sh"
-        env:
-          workdir: ${workdir}
     - command: archive.targz_pack
       params:
         target: burn_in_tags_gen.tgz
@@ -1032,8 +981,6 @@ functions:
         binary: bash
         args:
           - "./src/evergreen/randomized_multiversion_tasks_generate.sh"
-        env:
-          workdir: ${workdir}
 
     - *do_multiversion_setup
     - command: subprocess.exec
@@ -1041,8 +988,6 @@ functions:
         binary: bash
         args:
           - "./src/evergreen/randomized_multiversion_tasks_generate_exclude_tags.sh"
-        env:
-          workdir: ${workdir}
     - command: archive.targz_pack
       params:
         target: generate_tasks_config.tgz
@@ -1091,8 +1036,6 @@ functions:
         binary: bash
         args:
           - "./src/evergreen/resmoke_tasks_generate.sh"
-        env:
-          workdir: ${workdir}
 
     - command: archive.targz_pack
       params:
@@ -1202,8 +1145,6 @@ functions:
         binary: bash
         args:
           - "src/evergreen/scons_lint.sh"
-        env:
-          workdir: ${workdir}
 
   "scons compile":
     - *f_expansions_write
@@ -1213,9 +1154,6 @@ functions:
         binary: bash
         args:
           - "src/evergreen/scons_compile.sh"
-        env:
-          workdir: ${workdir}
-          patch_compile_flags: ${patch_compile_flags}
 
   "generate compile expansions":
     - *f_expansions_write
@@ -1224,8 +1162,6 @@ functions:
         binary: bash
         args:
           - "src/evergreen/functions/compile_expansions_generate.sh"
-        env:
-          workdir: ${workdir}
 
   "apply compile expansions":
     - command: expansions.update
@@ -1250,8 +1186,6 @@ functions:
         binary: bash
         args:
           - "./src/evergreen/do_jepsen_setup/nodes.sh"
-        env:
-          workdir: ${workdir}
     - command: subprocess.exec
       params:
         binary: bash
@@ -1267,15 +1201,11 @@ functions:
         binary: bash
         args:
           - "./src/evergreen/jepsen_test_run.sh"
-        env:
-          workdir: ${workdir}
     - command: subprocess.exec
       params:
         binary: bash
         args:
           - "./src/evergreen/jepsen_test_fail.sh"
-        env:
-          workdir: ${workdir}
 
   "load aws test credentials":
     - *f_expansions_write
@@ -1285,8 +1215,6 @@ functions:
         silent: true
         args:
           - "./src/evergreen/functions/aws_test_credentials_load.sh"
-        env:
-          workdir: ${workdir}
 
 
   "generate explicit multiversion tasks":
@@ -1308,8 +1236,6 @@ functions:
         binary: bash
         args:
           - "./src/evergreen/explicit_multiversion_tasks_generate.sh"
-        env:
-          workdir: ${workdir}
 
     - command: archive.targz_pack
       params:
@@ -1363,8 +1289,6 @@ functions:
         binary: bash
         args:
           - "./src/evergreen/implicit_multiversions_tasks_generate.sh"
-        env:
-          workdir: ${workdir}
 
     - command: archive.targz_pack
       params:
@@ -1416,8 +1340,6 @@ functions:
         binary: bash
         args:
           - "./src/evergreen/fuzzer_tasks_generate.sh"
-        env:
-          workdir: ${workdir}
 
     - command: archive.targz_pack
       params:
@@ -1455,8 +1377,6 @@ functions:
         binary: bash
         args:
           - "./src/evergreen/jstestfuzz_setup.sh"
-        env:
-          workdir: ${workdir}
 
   "lint fuzzer sanity patch":
     - *f_expansions_write
@@ -1466,8 +1386,6 @@ functions:
         binary: bash
         args:
           - "./src/evergreen/lint_fuzzer_sanity_patch.sh"
-        env:
-          workdir: ${workdir}
 
   "lint fuzzer sanity all":
     - *f_expansions_write
@@ -1477,8 +1395,6 @@ functions:
         binary: bash
         args:
           - "./src/evergreen/lint_fuzzer_sanity_all.sh"
-        env:
-          workdir: ${workdir}
 
   # Used by generator
   "run jstestfuzz":
@@ -1495,16 +1411,12 @@ functions:
         binary: bash
         args:
           - "./src/evergreen/jstestfuzz_run.sh"
-        env:
-          workdir: ${workdir}
     # TODO SERVER-57161 remove this touch command
     - command: subprocess.exec
       params:
         binary: touch
         args:
           - "./src/jstestfuzz/out/placeholder.js"
-        env:
-          workdir: ${workdir}
     - command: archive.targz_pack
       params:
         target: "jstests.tgz"
@@ -1531,8 +1443,6 @@ functions:
         binary: bash
         args:
           - "./src/evergreen/idl_tests_run.sh"
-        env:
-          workdir: ${workdir}
 
   "run powercycle test":
     - *f_expansions_write
@@ -1542,8 +1452,6 @@ functions:
         binary: bash
         args:
           - "./src/evergreen/powercycle_run_test.sh"
-        env:
-          workdir: ${workdir}
 
     - command: expansions.update
       params:
@@ -1562,16 +1470,12 @@ functions:
         binary: bash
         args:
           - "./src/evergreen/powercycle_ssh_failure_exit.sh"
-        env:
-          workdir: ${workdir}
     - command: subprocess.exec
       type: test
       params:
         binary: bash
         args:
           - "./src/evergreen/powercycle_exit.sh"
-        env:
-          workdir: ${workdir}
 
   "run packager.py":
     - *f_expansions_write
@@ -1580,8 +1484,6 @@ functions:
         binary: bash
         args:
           - "./src/evergreen/packager.py_run.sh"
-        env:
-          workdir: ${workdir}
 
   "do snmp setup":
     command: subprocess.exec
@@ -1620,8 +1522,6 @@ functions:
         binary: bash
         args:
           - "./src/evergreen/kitchen_run.sh"
-        env:
-          workdir: ${workdir}
 
   "set up EC2 instance": &set_up_ec2_instance
 
@@ -1646,8 +1546,6 @@ functions:
         binary: bash
         args:
           - "./src/evergreen/powercycle_check_host.sh"
-        env:
-          workdir: ${workdir}
 
     - command: expansions.update
       params:
@@ -1659,8 +1557,6 @@ functions:
         binary: bash
         args:
           - "./src/evergreen/powercycle_setup_host.sh"
-        env:
-          workdir: ${workdir}
 
   ### Process & archive remote EC2 artifacts ###
   "save powercycle artifacts": &save_powercycle_artifacts
@@ -1669,8 +1565,6 @@ functions:
       binary: bash
       args:
         - "./src/evergreen/powercycle_save_artifacts.sh"
-      env:
-        workdir: ${workdir}
 
   "archive remote EC2 artifacts": &archive_remote_ec2_artifacts
     command: s3.put
@@ -1711,8 +1605,6 @@ functions:
       binary: bash
       args:
         - "./src/evergreen/local_client_logs_tar.sh"
-      env:
-        workdir: ${workdir}
 
   "archive local client logs": &archive_local_client_logs
     command: s3.put
@@ -1866,8 +1758,6 @@ functions:
       binary: bash
       args:
         - "./src/evergreen/failed_unittests_gather.sh"
-      env:
-        workdir: ${workdir}
 
   "tar failed unittests": &tar_failed_unittests
     command: archive.targz_pack
@@ -1933,8 +1823,6 @@ functions:
       binary: bash
       args:
         - "./src/evergreen/hang_analyzer.sh"
-      env:
-        workdir: ${workdir}
 
   "wait for resmoke to shutdown":
     command: subprocess.exec
@@ -2084,8 +1972,6 @@ functions:
         binary: bash
         args:
           - "./src/evergreen/scons_splunk.sh"
-        env:
-          workdir: ${workdir}
 
   "attach report":
     command: attach.results
@@ -2107,8 +1993,6 @@ functions:
         binary: bash
         args:
           - "./src/evergreen/wiki_page.sh"
-        env:
-          workdir: ${workdir}
     - command: attach.artifacts
       params:
         files:
@@ -2206,8 +2090,6 @@ tasks:
         binary: bash
         args:
           - "src/evergreen/gen_feature_flags.sh"
-        env:
-          workdir: ${workdir}
 
     - command: archive.targz_pack
       params:
@@ -2292,8 +2174,6 @@ tasks:
         binary: bash
         args:
           - "./src/evergreen/ninja_compile.sh"
-        env:
-          workdir: ${workdir}
 
 - name: compile_ninja_next
   commands:
@@ -2313,8 +2193,6 @@ tasks:
         binary: bash
         args:
           - "./src/evergreen/ninja_compile.sh"
-        env:
-          workdir: ${workdir}
 
 - name: compile_build_tools_next
   commands:
@@ -2333,8 +2211,6 @@ tasks:
         binary: bash
         args:
           - "src/evergreen/libdeps_setup.sh"
-        env:
-          workdir: ${workdir}
 
     - func: "scons compile"
       vars:
@@ -2349,8 +2225,6 @@ tasks:
         binary: bash
         args:
           - "src/evergreen/libdeps_run.sh"
-        env:
-          workdir: ${workdir}
 
     - command: s3.put
       params:
@@ -2551,8 +2425,6 @@ tasks:
         binary: bash
         args:
           - "src/evergreen/embedded_sdk_build_cdriver.sh"
-        env:
-          workdir: ${workdir}
 
 - name: embedded_sdk_install_dev
   depends_on:
@@ -2586,8 +2458,6 @@ tasks:
         binary: bash
         args:
           - "src/evergreen/embedded_sdk_s3_tar.sh"
-        env:
-          workdir: ${workdir}
 
     # Upload it so we can download from EVG.
     - command: s3.put
@@ -2630,8 +2500,6 @@ tasks:
         binary: bash
         args:
           - "src/evergreen/embedded_sdk_tests_s3_tar.sh"
-        env:
-          workdir: ${workdir}
 
     # Upload it so we can download from EVG.
     - command: s3.put
@@ -2657,15 +2525,11 @@ tasks:
         binary: bash
         args:
           - "src/evergreen/embedded_sdk_run_tests.sh"
-        env:
-          workdir: ${workdir}
     - command: subprocess.exec
       params:
         binary: bash
         args:
           - "src/evergreen/embedded_sdk_run_tests_post.sh"
-        env:
-          workdir: ${workdir}
 
 - name: embedded_sdk_s3_put_latest
   depends_on:
@@ -2724,8 +2588,6 @@ tasks:
         binary: bash
         args:
           - "src/evergreen/stitch_support_create_lib_tar.sh"
-        env:
-          workdir: ${workdir}
     - command: s3.put
       params:
         aws_key: ${aws_key}
@@ -2765,8 +2627,6 @@ tasks:
         binary: bash
         args:
           - "src/evergreen/stitch_support_run_tests.sh"
-        env:
-          workdir: ${workdir}
 
 - name: compile_benchmarks
   depends_on: []
@@ -2890,8 +2750,6 @@ tasks:
       binary: bash
       args:
         - "src/evergreen/lint_yaml.sh"
-      env:
-        workdir: ${workdir}
 
 - name: lint_shellscripts
   commands:
@@ -2931,8 +2789,6 @@ tasks:
         binary: bash
         args:
           - "src/evergreen/check_idl_compat.sh"
-        env:
-          workdir: ${workdir}
 
 - name: burn_in_tests_gen
   commands:
@@ -2949,8 +2805,6 @@ tasks:
       binary: bash
       args:
         - "src/evergreen/burn_in_tests.sh"
-      env:
-        workdir: ${workdir}
   - command: archive.targz_pack
     params:
       target: src/burn_in_tests_gen.tgz
@@ -2989,8 +2843,6 @@ tasks:
       binary: bash
       args:
         - "src/evergreen/burn_in_tests_multiversion.sh"
-      env:
-        workdir: ${workdir}
 
   - command: archive.targz_pack
     params:
@@ -4478,8 +4330,6 @@ tasks:
       binary: bash
       args:
         - "src/evergreen/external_auth_pip.sh"
-      env:
-        workdir: ${workdir}
   - func: "run tests"
     vars:
       resmoke_args: --suites=external_auth --excludeWithAnyTags=requires_domain_controller --storageEngine=wiredTiger
@@ -4496,15 +4346,11 @@ tasks:
       silent: true
       args:
         - "src/evergreen/external_auth_aws_setup.sh"
-      env:
-        workdir: ${workdir}
   - command: subprocess.exec
     params:
       binary: bash
       args:
         - "src/evergreen/external_auth_aws_pip.sh"
-      env:
-        workdir: ${workdir}
   - func: "run tests"
     vars:
       resmoke_args: --suites=external_auth_aws --storageEngine=wiredTiger
@@ -6277,16 +6123,12 @@ tasks:
       silent: true
       args:
         - "src/evergreen/blackduck_setup.sh"
-      env:
-        workdir: ${workdir}
   - command: subprocess.exec
     type: test
     params:
       binary: bash
       args:
         - "src/evergreen/blackduck_hub.sh"
-      env:
-        workdir: ${workdir}
 
 - name: tla_plus
   commands:
@@ -6361,8 +6203,6 @@ tasks:
         binary: bash
         args:
           - "src/evergreen/package.sh"
-        env:
-          workdir: ${workdir}
     - command: s3.put
       params:
         aws_key: ${aws_key}
@@ -6512,8 +6352,6 @@ tasks:
         binary: bash
         args:
           - "./src/evergreen/packages_publish.sh"
-        env:
-          workdir: ${workdir}
 
 - name: push
   tags: ["publish"]
@@ -6577,8 +6415,6 @@ tasks:
         binary: bash
         args:
           - "./src/evergreen/notary_client_run.sh"
-        env:
-          workdir: ${workdir}
 
     # Put the binaries tarball/zipfile
     - command: s3.put
@@ -7127,8 +6963,6 @@ tasks:
       binary: bash
       args:
         - "./src/evergreen/commit_message_validate.sh"
-      env:
-        workdir: ${workdir}
 
 - name: check_for_todos
   exec_timeout_secs: 600 # 10 minute timeout
@@ -7144,8 +6978,6 @@ tasks:
         binary: bash
         args:
           - "./src/evergreen/todos_check.sh"
-        env:
-          workdir: ${workdir}
 
 - <<: *task_template
   name: mqlrun
diff --git a/evergreen/functions/venv_setup.sh b/evergreen/functions/venv_setup.sh
index 7eb6c3d14a2..0a901296aee 100644
--- a/evergreen/functions/venv_setup.sh
+++ b/evergreen/functions/venv_setup.sh
@@ -1,10 +1,11 @@
 # exit immediately if virtualenv is not found
 set -o errexit
 
-evergreen_dir="$(cd "$(dirname "${BASH_SOURCE[0]}")" >/dev/null 2>&1 && pwd)"
-. "$evergreen_dir/../prelude_python.sh"
+evergreen_dir="$(cd "$(dirname "${BASH_SOURCE[0]}")" >/dev/null 2>&1 && pwd)/.."
+. "$evergreen_dir/prelude_workdir.sh"
+. "$evergreen_dir/prelude_python.sh"
 
-python_loc=$(which ${python:-/opt/mongodbtoolchain/v3/bin/python3})
+python_loc=$(which ${python})
 venv_dir="${workdir}/venv"
 if [ -d "$venv_dir" ]; then
   exit 0
@@ -34,7 +35,7 @@ toolchain_txt="$pip_dir/toolchain-requirements.txt"
 
 # the whole prelude cannot be imported because it requires pyyaml to be
 # installed, which happens just below.
-. "$evergreen_dir/../prelude_venv.sh"
+. "$evergreen_dir/prelude_venv.sh"
 
 activate_venv
 echo "Upgrading pip to 21.0.1"
diff --git a/evergreen/prelude.sh b/evergreen/prelude.sh
index 86f41a53c44..a44b69e7a0a 100755
--- a/evergreen/prelude.sh
+++ b/evergreen/prelude.sh
@@ -2,20 +2,12 @@ if [[ "$0" == *"/evergreen/prelude.sh" ]]; then
   echo "ERROR: do not execute this script. source it instead. ie: . prelude.sh"
   exit 1
 fi
+set -o errexit
 
 # path the directory that contains this script.
 evergreen_dir="$(cd "$(dirname "${BASH_SOURCE[0]}")" >/dev/null 2>&1 && pwd)"
 
-# bootstrapping python assumes that the user has not cd'd before the prelude.
-# Ensure that here.
-calculated_workdir=$(cd "$evergreen_dir/../.." && echo $PWD)
-if [ "$PWD" != "$calculated_workdir" ]; then
-  echo "ERROR: Your script changed directory before loading prelude.sh. Don't do that"
-  echo "\$PWD: $PWD"
-  echo "\$calculated_workdir: $calculated_workdir"
-  exit 1
-fi
-
+. "$evergreen_dir/prelude_workdir.sh"
 . "$evergreen_dir/prelude_python.sh"
 . "$evergreen_dir/prelude_venv.sh"
 
@@ -79,3 +71,4 @@ function set_sudo {
     set -o errexit
   fi
 }
+set +o errexit
diff --git a/evergreen/prelude_venv.sh b/evergreen/prelude_venv.sh
index 953f4e63d02..728e097ffe0 100644
--- a/evergreen/prelude_venv.sh
+++ b/evergreen/prelude_venv.sh
@@ -13,7 +13,10 @@ function activate_venv {
     fi
     python=python
   else
-    python=${python:-/opt/mongodbtoolchain/v3/bin/python3}
+    if [ -z "$python" ]; then
+      echo "\$python is unset. This should never happen"
+    fi
+    python=${python}
   fi
 
   if [ "Windows_NT" = "$OS" ]; then
diff --git a/evergreen/prelude_workdir.sh b/evergreen/prelude_workdir.sh
new file mode 100644
index 00000000000..2e39ba1f3b8
--- /dev/null
+++ b/evergreen/prelude_workdir.sh
@@ -0,0 +1,26 @@
+calculated_workdir=$(cd "$evergreen_dir/../.." && echo "$PWD")
+pwd_cygpath="$PWD"
+if [ "Windows_NT" = "$OS" ]; then
+  calculated_workdir=$(cygpath -w "$calculated_workdir")
+  pwd_cygpath=$(cygpath -w "$pwd_cygpath")
+fi
+if [ -z "$workdir" ]; then
+  workdir="$calculated_workdir"
+
+# skip this test on Windows. The directories will never match due to the many
+# different path types present on Windows+Cygwin
+elif [ "$workdir" != "$calculated_workdir" ] && [ "Windows_NT" != "$OS" ]; then
+  # if you move the checkout directory (ex: simple project config project),
+  # then this assertion will fail in the future. You need to update
+  # calculated_workdir, and all the relative directories in this file.
+  echo "\$workdir was specified, but didn't match \$calculated_workdir. Did the directory structure change? Update prelude.sh"
+  echo "\$workdir: $workdir"
+  echo "\$calculated_workdir: $calculated_workdir"
+  exit 1
+fi
+if [ "$pwd_cygpath" != "$calculated_workdir" ]; then
+  echo "ERROR: Your script changed directory before loading prelude.sh. Don't do that"
+  echo "\$PWD: $PWD"
+  echo "\$calculated_workdir: $calculated_workdir"
+  exit 1
+fi