{"id":19,"date":"2022-05-04T14:52:17","date_gmt":"2022-05-04T19:52:17","guid":{"rendered":"https:\/\/jcshort.net\/?p=19"},"modified":"2026-06-04T10:50:46","modified_gmt":"2026-06-04T15:50:46","slug":"context-specific-tool-management-with-direnv-asdf","status":"publish","type":"post","link":"https:\/\/jcshort.net\/?p=19","title":{"rendered":"Context-specific tool management with direnv"},"content":{"rendered":"\n
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I’ve tried juggling virtualenvs by hand. Who has the time to manually activate and deactivate when jumping between projects?<\/p>\n\n\n\n

I’ve tried language-specific version managers. Sometimes they work. Sometimes you have to wait double-digit seconds for re-shimming.<\/p>\n\n\n\n

I’ve tried using tool-specific wrappers like tfenv. The cognitive burden increases exponentially with each one added to the pile.<\/p>\n<\/div><\/div>\n\n\n\n

<\/p>\n\n\n\n

But none of them solve the entire problem. Maybe this project needs a specific version of Python. Maybe that one is stuck on a weird version of Terraform. Yet another is using a deprecated Helm version, but the package manager only has the latest patch in that series.<\/p>\n\n\n\n

Direnv<\/a> does a lot out of the box, but its strength is configuring projects to use an available version of a tool, it does not provide those versions itself. Some languages have competent version manager tools that are worth using, but operational tools like terraform and kubectl generally lack version managers.<\/p>\n\n\n\n

That’s where asdf<\/a> comes in. Not only is it a joy to type, when combined with direnv it’s actually fast<\/em>. Putting tool paths into a direnv include means no more waiting for slow re-shimming, running commands manually, or re-hashing your shell cache.<\/p>\n\n\n\n

It’s as simple as:<\/p>\n\n\n

brew install direnv asdf\ndirenv hook\nasdf plugin add direnv\nasdf direnv setup --version system<\/code><\/span><\/pre>\n\n\n
You can then add use asdf<\/code> to your .envrc<\/code> file, and the plugin will modify PATH based on .tool-versions<\/code>, e.g.:<\/p>\n\n\n
$ echo<\/span> \"use asdf\"<\/span> >> project\/.envrc\n$ direnv allow project\n$ cat << EOF > project\/.tool-versions\nhelm 2.16<\/span>.3<\/span>\nkubectl 1.20<\/span>.15<\/span>\nterraform 0.14<\/span>.11<\/span>\nEOF<\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
Now, not only is the python virtualenv automatically activated and deactivated, so are those tools:<\/p>\n\n\n
> $ cd project\ndirenv<\/span>: loading ~\/project\/<\/span>.envrc\ndirenv<\/span>: using asdf\ndirenv<\/span>: loading ~\/.cache\/<\/span>asdf-direnv\/env\/2471675625<\/span>-973451084<\/span>-2702573808<\/span>-1004245725<\/span>\ndirenv<\/span>: using asdf terraform 0.14<\/span>.11<\/span>\ndirenv<\/span>: using asdf kubectl 1.20<\/span>.15<\/span>\ndirenv<\/span>: using asdf helm 2.16<\/span>.3<\/span>\ndirenv<\/span>: export<\/span> ~PATH<\/code><\/span>Code language:<\/span> JavaScript<\/span> (<\/span>javascript<\/span>)<\/span><\/small><\/pre>\n\n\n
<\/p>\n\n\n\n
But what about virtual environments?<\/strong><\/p>\n\n\n\n
asdf is great for managing tool versions, but some tools have baggage<\/em>.  Like python virtual environments.  For that, we’ll need something a bit more specialized: pyenv.<\/p>\n\n\n
$ brew install pyenv\n$ echo<\/span> _PYENV_DIR=\"$(pyenv prefix)\"<\/span> >> ~\/.zshrc\n$ source ~\/.zshrc<\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
direnv “layout” mode places files (such as virtualenvs) into the ~\/.direnv<\/code> folder within the project:<\/p>\n\n\n
$ echo \"layout pyenv 3.10.10\"<\/span> >> project\/.envrc\n$ direnv allow project\n$ cd project\ndirenv<\/span>: loading ~\/project\/<\/span>.envrc\ndirenv<\/span>: export<\/span> +PYENV_VERSION +VIRTUAL_ENV ~PATH\n\n$ which python\n\/redacted\/project\/.direnv\/python-3.10<\/span>.10<\/span>\/bin\/python<\/code><\/span>Code language:<\/span> JavaScript<\/span> (<\/span>javascript<\/span>)<\/span><\/small><\/pre>\n\n\n
I’ve tried juggling virtualenvs by hand. Who has the time to manually activate and deactivate when jumping between projects? I’ve tried language-specific version managers. Sometimes they work. Sometimes you have to wait double-digit seconds for re-shimming. I’ve tried using tool-specific wrappers like tfenv. The cognitive burden increases exponentially with each one added to the pile. […]<\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_genesis_hide_title":false,"_genesis_hide_breadcrumbs":false,"_genesis_hide_singular_image":false,"_genesis_hide_footer_widgets":false,"_genesis_custom_body_class":"","_genesis_custom_post_class":"","_genesis_layout":"","footnotes":""},"categories":[1],"tags":[],"class_list":["post-19","post","type-post","status-publish","format-standard","category-tech","entry"],"featured_image_src":null,"featured_image_src_square":null,"author_info":{"display_name":"jshort","author_link":"https:\/\/jcshort.net\/?author=2"},"_links":{"self":[{"href":"https:\/\/jcshort.net\/index.php?rest_route=\/wp\/v2\/posts\/19","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/jcshort.net\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/jcshort.net\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/jcshort.net\/index.php?rest_route=\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/jcshort.net\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=19"}],"version-history":[{"count":0,"href":"https:\/\/jcshort.net\/index.php?rest_route=\/wp\/v2\/posts\/19\/revisions"}],"wp:attachment":[{"href":"https:\/\/jcshort.net\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=19"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/jcshort.net\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=19"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/jcshort.net\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=19"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}
Python packages can be managed normally from here via pip<\/code>.  Similar plugins exist for node, ruby, etc, and can be found in the direnv stdlib man page<\/a>.<\/p>\n","protected":false},"excerpt":{"rendered":"