feat(python): add support for creating python .venv and installing dependencies by mwbrooks · Pull Request #346 · slackapi/slack-cli

mwbrooks · 2026-02-20T19:45:55Z

Changelog

Updated the slack create and slack init commands to support creating a Python virtual environment (.venv) when it doesn't exist and installing the project's dependencies from requirements.txt and pyproject.toml.

Summary

This pull request adds support for creating a Python virtual environment when it doesn't already exist and installs the dependencies defined in requirements.txt and pyproject.toml.

Out-of-scope:

Activating the virtual environment on each Slack CLI commands. We can follow-up in another PR with that feature.

Known issues:

When a pyproject.toml doesn't include a [project] section or dependencies array, the Slack CLI will display an error. It gracefully fails by continuing with the installation process for requirements.txt. However, I think we have an opportunity to update the Slack CLI to display a "Skipped updating pyproject.toml: no dependencies array" message instead of an error. That can be handled in a follow-up PR.

Related PRs:

Preview

Example of an app with a valid pyproject.toml:

Example of an app with an incomplete pyproject.toml:

Reviewers

Example of an app with a valid pyproject.toml:

$ lack create my-test-app/
# → Select "AI Agent App"
# → Select "Bolt for Python"

# Validate output:
# → Confirm: "Created virtual environment at .venv"
# → Confirm: "Installed dependencies from pyproject.toml"
# → Confirm: "Installed dependencies from requirements.txt"
# → Confirm: No errors

# Validate .env
$ ls -al my-test-app/.venv
# → Confirm: Exists

# Test app dependencies installed
$ cd my-test-app/
$ source .venv/bin/activate
$ lack run
# → Confirm: App starts

# Clean up
$ cd ../
$ rm -rf my-test-app/

Example of an app with an incomplete pyproject.toml:

$ lack create my-test-app/
# → Select "Starter App"
# → Select "Bolt for Python"

# Validate output:
# → Confirm: "Created virtual environment at .venv"
# → Confirm: "Error updating pyproject.toml: pyproject.toml missing project section"
# → Confirm: "Installed dependencies from pyproject.toml"
# → Confirm: "Installed dependencies from requirements.txt"

# Validate .env
$ ls -al my-test-app/.venv
# → Confirm: Exists

# Test app dependencies installed
$ cd my-test-app/
$ source .venv/bin/activate
$ lack run
# → Confirm: App starts

# Clean up
$ cd ../
$ rm -rf my-test-app/

Requirements

I've read and understood the Contributing Guidelines and have done my best effort to follow them.
I've read and agree to the Code of Conduct.

Swap pip install order so pyproject.toml is installed first to set up the project package, then requirements.txt pins take precedence as the lockfile.

…for pip

codecov · 2026-02-20T23:01:21Z

Codecov Report

❌ Patch coverage is 71.60494% with 23 lines in your changes missing coverage. Please review.
✅ Project coverage is 64.68%. Comparing base (44cb5f9) to head (abe12d0).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
internal/runtime/python/python.go	71.25%	14 Missing and 9 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #346      +/-   ##
==========================================
- Coverage   64.69%   64.68%   -0.01%     
==========================================
  Files         213      213              
  Lines       17967    18018      +51     
==========================================
+ Hits        11623    11655      +32     
- Misses       5266     5276      +10     
- Partials     1078     1087       +9

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

Clarify error messages in installPyProjectToml to include "updating pyproject.toml" context, and remove early return on file update errors so pip install is attempted regardless.

mwbrooks

Comments for the kind folks 👓

mwbrooks · 2026-02-20T23:35:23Z

internal/runtime/python/python.go

 	if !exists {
 		err := fmt.Errorf("pyproject.toml missing project section")
-		return fmt.Sprintf("Error: %s", err), err
+		return fmt.Sprintf("Error updating pyproject.toml: %s", err), err


note: Improving error messages when there is an error adding slack-cli-hooks to pyproject.toml.

Route createVirtualEnvironment and runPipInstall through HookExecutor instead of os/exec, matching the npm runtime pattern. This makes the functions testable with the mock filesystem. Also add missing AddDefaultMocks call, remove stale test cases, and fix assertion strings.

mwbrooks · 2026-02-21T00:25:32Z

internal/runtime/python/python.go

+	hookScript := hooks.HookScript{
+		Name:    "CreateVirtualEnvironment",
+		Command: fmt.Sprintf("%s -m venv .venv", getPythonExecutable()),
+	}
+	stdout := bytes.Buffer{}
+	hookExecOpts := hooks.HookExecOpts{
+		Hook:      hookScript,
+		Stdout:    &stdout,
+		Directory: projectDirPath,
+	}
+	_, err := hookExecutor.Execute(ctx, hookExecOpts)


note: While it's verbose, we use the hookExecutor so that we can mock the exec calls during tests. This is how we also handle npm install.

@mwbrooks This is a solid approach! IIRC the default hook execution protocol is used here since we don't have hooks loaded at this point, and the testing approach is great!

I'm hesitant on the CreateVirtualEnvironment hook name right now - it's almost an extension of a shared InstallDependencies to me. Rambles but this isn't exposed in configurations so for iteration ongoing 📚

zimeg

When a pyproject.toml doesn't include a [project] section or dependencies array, the Slack CLI will display an error. It gracefully fails by continuing with the installation process for requirements.txt.

@mwbrooks Thanks for calling this out! I think the current approach is solid with your updates to sample apps that add "pyproject.toml" files - this seems sometimes recommended alongside "requirements.txt" for pinned dependencies but I'm not sure how frequent that is? I suggest we remove "requirements.txt" but we should decide later!

I'm approving now after testing well on the create experience and leaving a few notes! FWIW this adds multiple seconds to this step - 5 seconds on a solid work machine and 55 seconds on the Windows laptop I keep. The .venv path seems standard of "uv" and "pip" but that time might feel extra if "uv" benchmarks are true! 🚢 💨

This does address the extra step I often forget when switching between javascsript and python so please know these notes are rambles. Let's get this merged for next release 🎁 🐍 ✨

zimeg · 2026-02-24T22:16:35Z

cmd/project/init.go

 			"- Deno:    Supported",
 			"- Node.js: Supported",
-			"- Python:  Unsupported",
+			"- Python:  Supported",


🐍 praise: Such a nice diff to find!

zimeg · 2026-02-24T22:27:51Z

internal/runtime/python/python.go

-		var projectDirPathRel, _ = getProjectDirRelPath(os, os.GetExecutionDir(), projectDirPath)
-
-		outputs = append(outputs, fmt.Sprintf("Manually setup a %s", style.Highlight("Python virtual environment")))
-		if projectDirPathRel != "." {
-			outputs = append(outputs, fmt.Sprintf("  Change into the project: %s", style.CommandText(fmt.Sprintf("cd %s%s", filepath.Base(projectDirPathRel), string(filepath.Separator)))))
-		}
-		outputs = append(outputs, fmt.Sprintf("  Create virtual environment: %s", style.CommandText("python3 -m venv .venv")))
-		outputs = append(outputs, fmt.Sprintf("  Activate virtual environment: %s", style.CommandText(activateVirtualEnv)))
-
-		// Provide appropriate install command based on which file exists
-		if hasRequirementsTxt {
-			outputs = append(outputs, fmt.Sprintf("  Install project dependencies: %s", style.CommandText("pip install -r requirements.txt")))
-		}
-		if hasPyProjectToml {
-			outputs = append(outputs, fmt.Sprintf("  Install project dependencies: %s", style.CommandText("pip install -e .")))
-		}
+	// Ensure at least one dependency file exists
+	if !hasRequirementsTxt && !hasPyProjectToml {
+		err := fmt.Errorf("no Python dependency file found (requirements.txt or pyproject.toml)")
+		return fmt.Sprintf("Error: %s", err), err
+	}

-		outputs = append(outputs, fmt.Sprintf("  Learn more: %s", style.Underline("https://docs.python.org/3/tutorial/venv.html")))


🪓 praise: Farewell setup steps! I notice #347 brings changes to make the activation step automatic too! Really neat!

zimeg · 2026-02-24T22:32:35Z

internal/runtime/python/python.go

+	hookScript := hooks.HookScript{
+		Name:    "CreateVirtualEnvironment",
+		Command: fmt.Sprintf("%s -m venv .venv", getPythonExecutable()),
+	}
+	stdout := bytes.Buffer{}
+	hookExecOpts := hooks.HookExecOpts{
+		Hook:      hookScript,
+		Stdout:    &stdout,
+		Directory: projectDirPath,
+	}
+	_, err := hookExecutor.Execute(ctx, hookExecOpts)


@mwbrooks This is a solid approach! IIRC the default hook execution protocol is used here since we don't have hooks loaded at this point, and the testing approach is great!

I'm hesitant on the CreateVirtualEnvironment hook name right now - it's almost an extension of a shared InstallDependencies to me. Rambles but this isn't exposed in configurations so for iteration ongoing 📚

zimeg · 2026-02-24T22:33:51Z

internal/runtime/python/python.go

-			firstErr = errs[0]
+	// Create virtual environment if it doesn't exist
+	if !venvExists(fs, venvPath) {
+		ios.PrintDebug(ctx, "Creating Python virtual environment")


🌟 praise: Debugging the start of something and printing the end is a super fascinating pattern!

zimeg · 2026-02-24T22:55:50Z

internal/runtime/python/python_test.go

+			existingContent: `[project]
+name = "my-app"
+dependencies = ["pytest==8.3.2"]`,


🧪 suggestion: We might want to follow up to support something as following, but I also understand that the initial update is most meaningful since this file can be modified to preference afterward:

[project.optional-dependencies] cli = [ "slack-cli-hooks<1.0.0", ]

🔗 https://packaging.python.org/en/latest/guides/writing-pyproject-toml/#dependencies-and-requirements

👁️‍🗨️ note: I do fear that'd complicate our current InstallProjectDependencies hook to require for certain cases:

$ pip install -e ".[cli]"

zimeg · 2026-02-24T22:59:14Z

internal/runtime/python/python.go

+	return output, nil
+}
+
 // installRequirementsTxt handles adding slack-cli-hooks to requirements.txt


🐣 note: I found the test cases confusing for these "install" functions that are also updating the requirements. Not a blocker for this PR, but we might change this to be something as:

initializeAndInstallRequirementsTxt

If changes are ongoing? Apologies for calling this out in an unrelated PR too!

mwbrooks added 5 commits February 20, 2026 10:24

feat(python): add support for creating and activating venv

9d6e1d9

fix(python): install pyproject.toml before requirements.txt

665e23c

Swap pip install order so pyproject.toml is installed first to set up the project package, then requirements.txt pins take precedence as the lockfile.

chore(cmd): remove venv detail from init command description

9008d02

fix(python): use correct python executable on Windows for venv creation

51030ee

chore(python): add comment explaining venv activation is unnecessary …

6e6ba42

…for pip

mwbrooks self-assigned this Feb 20, 2026

mwbrooks added enhancement M-T: A feature request for new functionality semver:minor Use on pull requests to describe the release version increment area:bolt-python Related to github.com/slackapi/bolt-python changelog Use on updates to be included in the release notes labels Feb 20, 2026

mwbrooks added this to the Next Release milestone Feb 20, 2026

mwbrooks added 4 commits February 20, 2026 14:04

chore(python): fix gofmt formatting in python_test.go

cf35c5c

chore(python): move venv creation message to debug output

bff1d8c

chore(python): move dependency install messages to debug output

b0f0050

chore(python): shorten install success messages and highlight filenames

e641b20

fix(python): improve error handling for dependency file updates

4324103

Clarify error messages in installPyProjectToml to include "updating pyproject.toml" context, and remove early return on file update errors so pip install is attempted regardless.

mwbrooks changed the title ~~feat(python): add support for creating and activating venv~~ feat(python): add support for creating a python .venv Feb 20, 2026

mwbrooks changed the title ~~feat(python): add support for creating a python .venv~~ feat(python): update 'create' and 'init' commands to support creating a python .venv Feb 20, 2026

mwbrooks changed the title ~~feat(python): update 'create' and 'init' commands to support creating a python .venv~~ feat(python): update 'create' and 'init' to support creating a python .venv Feb 20, 2026

mwbrooks changed the title ~~feat(python): update 'create' and 'init' to support creating a python .venv~~ feat(python): update 'create' and 'init' to support creating and installing python .venv Feb 20, 2026

mwbrooks changed the title ~~feat(python): update 'create' and 'init' to support creating and installing python .venv~~ feat(python): add support for creating python .venv and installing dependencies Feb 20, 2026

test: remove skipped test

3a76ba8

mwbrooks commented Feb 20, 2026

View reviewed changes

mwbrooks commented Feb 21, 2026

View reviewed changes

mwbrooks marked this pull request as ready for review February 21, 2026 00:33

mwbrooks requested a review from a team as a code owner February 21, 2026 00:33

zimeg added 2 commits February 24, 2026 14:05

Merge branch 'main' into mwbrooks-python-venv

409dc41

refactor: convert table tests to test case structs

60f4290

zimeg added 2 commits February 24, 2026 14:47

test: run os specific test cases

cbfbbe1

chore: merge w main

abe12d0

zimeg approved these changes Feb 27, 2026

View reviewed changes

zimeg merged commit 3417188 into main Feb 27, 2026
8 checks passed

zimeg deleted the mwbrooks-python-venv branch February 27, 2026 02:58

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mwbrooks commented Feb 20, 2026 •

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