feat(wsl2): auto-detect wsl2 and advise user

Author: noelmcloughlin

README.md

@@ -89,14 +89,14 @@ Optionally customize your project if needed:
 
 * pass arguments to linkml generators via 'config.yaml' configuration file;
 * pass supported environment variables via '.env.public' configuration file;
+* Set 'export JUST_TEMPDIR=/tmp' on WSL2.
 
 Setup your project
 
 ```shell
 cd my-awesome-schema  # using the folder example above
 just setup
 ```
-Note: Command `JUST_TEMPDIR=/tmp just setup` may be needed in certain cases [ref](https://github.com/casey/just/?tab=readme-ov-file#script-and-shebang-recipe-temporary-files).
 
 ### Step 3: Edit the schema
 

template/justfile

@@ -6,6 +6,9 @@
 
 # ============ Variables used in recipes ============
 
+# Detect WSL2 variable
+_wsl2_check := `[ -n "${WSL_INTEROP:-}" ] && [ -z "${JUST_TEMPDIR:-}" ] && echo "ERROR" || echo "OK"`
+
 # Load environment variables from config.public.mk or specified file
 set dotenv-load := true
 # set dotenv-filename := env_var_or_default("LINKML_ENVIRONMENT_FILENAME", "config.public.mk")
@@ -44,11 +47,36 @@ distrib_schema_path := "docs/schema"  # Directory for publishing schema artifact
 
 # List all commands as default command. The prefix "_" hides the command.
 _default: _status
+    @{{ if _wsl2_check == "ERROR" { "echo 'WSL2 detected: run export JUST_TEMPDIR=/tmp'" } else { "" } }}
     @just --list
 
+# WSL2 status check - warns but does not abort (safe to use in _status/_default)
+[private]
+_wsl2_status_check:
+    @if [ -n "${WSL_INTEROP:-}" ] && [ -z "${JUST_TEMPDIR:-}" ]; then \
+      echo "WARNING: WSL2 detected but JUST_TEMPDIR is not set."; \
+      echo "Shebang recipes will fail with 'Permission denied' errors."; \
+      echo "Fix: run 'export JUST_TEMPDIR=/tmp'"; \
+    fi
+
+# WSL2 compatibility check - fails early with helpful message
+[private]
+_wsl2_compat_check:
+    @if [ -n "${WSL_INTEROP:-}" ] && [ -z "${JUST_TEMPDIR:-}" ]; then \
+      echo "ERROR: WSL2 detected but JUST_TEMPDIR is not set."; \
+      echo "Shebang recipes will fail with 'Permission denied' errors."; \
+      echo ""; \
+      echo "Fix: run this command:"; \
+      echo ""; \
+      echo "  export JUST_TEMPDIR=/tmp"; \
+      echo ""; \
+      echo "Or add it to your ~/.bashrc for persistence."; \
+      exit 1; \
+    fi
+
 # Initialize a new project (use this for projects not yet under version control)
 [group('project management')]
-setup: _check-config _git-init install _git-add && _setup_part2
+setup: _wsl2_compat_check _check-config _git-init install _git-add && _setup_part2
   git commit -m "Initialise git with minimal project" -a || true
 
 _setup_part2: gen-project gen-doc
@@ -70,7 +98,7 @@ update: _update-template _update-linkml
 
 # Clean all generated files
 [group('project management')]
-clean: _clean_project
+clean: _wsl2_compat_check _clean_project
   rm -rf tmp
   rm -rf {{docdir}}/*.md
 
@@ -131,7 +159,7 @@ gen-project:
 # Hidden command to adjust the directory layout on upgrading a project
 # created with linkml-project-copier v0.1.x to v0.2.0 or newer.
 # Use with care! - It may not work for customized projects.
-_post_upgrade_v020: && _post_upgrade_v020py
+_post_upgrade_v020: _wsl2_compat_check && _post_upgrade_v020py
   mv docs/*.md docs/elements
 
 _post_upgrade_v020py:
@@ -160,7 +188,7 @@ _post_upgrade_v020py:
 # ============== Hidden internal recipes ==============
 
 # Show current project status
-_status: _check-config
+_status: _wsl2_status_check _check-config
   @echo "Project: {{schema_name}}"
   @echo "Source: {{source_schema_path}}"