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fix env_vars: preprend_path and append_path were doing the opposite #285

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fix env_vars: preprend_path and append_path were doing the opposite #285

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5a1d620
match env vars operation with user directive for append/prepend path
albestro Feb 27, 2026
7ad690b
refactor logic into envvars
albestro Mar 3, 2026
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57 changes: 57 additions & 0 deletions stackinator/etc/envvars.py
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Original file line number Diff line number Diff line change
Expand Up @@ -3,6 +3,7 @@
import argparse
import json
import os
import re
from enum import Enum
from typing import List, Optional

Expand Down Expand Up @@ -206,6 +207,11 @@ def is_list_var(name: str) -> bool:
return name in list_variables


class VarExpansionError(Exception):
def __init__(self, variable_name) -> None:
super().__init__(f'"{variable_name}" variable cannot be expanded')


class EnvVarSet:
"""
A set of environment variable updates.
Expand All @@ -219,6 +225,57 @@ def __init__(self):
# toggles whether post export commands will be generated
self._generate_post = True

@classmethod
def from_envvars(cls, input: dict, substitutions: dict):
def expand_vars(s):
def var_expansion(m: re.Match):
try:
return substitutions[m.group(1)]
except KeyError:
raise VarExpansionError(m.group(0))

return re.sub(r"\$@(\w+)@", var_expansion, s)

# TODO: one day this code will be revisited because we need to append_path
# or prepend_path to a variable that isn't in envvars.is_list_var
# On that day, extend the environments.yaml views:uenv:env_vars field
# to also accept a list of env var names to add to the blessed list of prefix paths

env = EnvVarSet()

for v in input.get("set", []):
((name, value),) = v.items()
if value is not None:
value = expand_vars(value)

# insist that the only 'set' operation on prefix variables is to unset/reset them
# this requires that users use append and prepend to build up the variables
if is_list_var(name) and value is not None:
raise RuntimeError(f"{name} is a prefix variable")
else:
if is_list_var(name):
env.set_list(name, [], EnvVarOp.SET)
else:
env.set_scalar(name, value)

for v in input.get("prepend_path", []):
((name, value),) = v.items()
if value is not None:
value = expand_vars(value)
if not is_list_var(name):
raise RuntimeError(f"{name} is not a known prefix path variable")
env.set_list(name, [value], EnvVarOp.PREPEND)

for v in input.get("append_path", []):
((name, value),) = v.items()
if value is not None:
value = expand_vars(value)
if not is_list_var(name):
raise RuntimeError(f"{name} is not a known prefix path variable")
env.set_list(name, [value], EnvVarOp.APPEND)

return env

@property
def lists(self):
return self._lists
Expand Down
68 changes: 13 additions & 55 deletions stackinator/recipe.py
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Original file line number Diff line number Diff line change
Expand Up @@ -6,7 +6,7 @@
import yaml

from . import cache, root_logger, schema, spack_util
from .etc import envvars
from .etc.envvars import EnvVarSet


class Recipe:
Expand Down Expand Up @@ -292,60 +292,18 @@ def environment_view_meta(self):
view_meta = {}
for _, env in self.environments.items():
for view in env["views"]:
# recipe authors can substitute the name of the view, the mount
# and view path into environment variables using '$@key@' where
# key is one of view_name, mount and view_path.
substitutions = {
"view_name": str(view["name"]),
"mount": str(self.mount),
"view_path": str(view["config"]["root"]),
}

def fill(s):
return re.sub(
r"\$@(\w+)@",
lambda m: substitutions.get(m.group(1), m.group(0)),
s,
)

ev_inputs = view["extra"]["env_vars"]
env = envvars.EnvVarSet()

# TODO: one day this code will be revisited because we need to append_path
# or prepend_path to a variable that isn't in envvars.is_list_var
# On that day, extend the environments.yaml views:uenv:env_vars field
# to also accept a list of env var names to add to the blessed list of prefix paths

for v in ev_inputs["set"]:
((name, value),) = v.items()
if value is not None:
value = fill(value)

# insist that the only 'set' operation on prefix variables is to unset/reset them
# this requires that users use append and prepend to build up the variables
if envvars.is_list_var(name) and value is not None:
raise RuntimeError(f"{name} in the {view['name']} view is a prefix variable.")
else:
if envvars.is_list_var(name):
env.set_list(name, [], envvars.EnvVarOp.SET)
else:
env.set_scalar(name, value)
for v in ev_inputs["prepend_path"]:
((name, value),) = v.items()
if value is not None:
value = fill(value)
if not envvars.is_list_var(name):
raise RuntimeError(f"{name} in the {view['name']} view is not a known prefix path variable")

env.set_list(name, [value], envvars.EnvVarOp.APPEND)
for v in ev_inputs["append_path"]:
((name, value),) = v.items()
if value is not None:
value = fill(value)
if not envvars.is_list_var(name):
raise RuntimeError(f"{name} in the {view['name']} view is not a known prefix path variable")

env.set_list(name, [value], envvars.EnvVarOp.PREPEND)
try:
# recipe authors can substitute the name of the view, the mount
# and view path into environment variables using '$@key@' where
# key is one of view_name, mount and view_path.
substitutions = {
"view_name": str(view["name"]),
"mount": str(self.mount),
"view_path": str(view["config"]["root"]),
}
env = EnvVarSet.from_envvars(view["extra"]["env_vars"], substitutions)
except Exception as err:
raise RuntimeError(f'In view "{view["name"]}": {err}')

view_meta[view["name"]] = {
"root": view["config"]["root"],
Expand Down