feat: capture pre-init Python environment in init telemetry

[FarhanAliRaza]

Snapshot virtualenv state and presence of pyproject.toml/requirements.txt before template scaffolding runs so the "init" event reflects the user's actual starting environment, not files the template created.

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Type of change

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• New feature (non-breaking change which adds functionality)

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Changes To Core Features:

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fixes ENG-9476

[greptile-apps]

Greptile Summary

This PR adds a get_init_environment() helper that snapshots whether the user is inside a virtualenv and whether pyproject.toml/requirements.txt exist, capturing this state before template scaffolding modifies the directory. The snapshot is then forwarded as event properties to the existing send("init", …) call.

• Adds is_in_virtualenv() (PEP 405 prefix comparison + VIRTUAL_ENV fallback) and get_init_environment() to telemetry.py, called in initialize_app before any scaffolding touches the filesystem.
• Extends the test suite with fixtures to control sys.prefix/sys.base_prefix/VIRTUAL_ENV and a temporary working directory, covering virtualenv detection and both dependency-file presence paths.

Confidence Score: 5/5

Safe to merge — the change is additive telemetry only and does not affect application init logic.

The snapshot is captured before scaffolding, passed through the existing properties merge path in _prepare_event, and is never persisted or used in any control flow.

reflex/utils/telemetry.py — the conda detection gap in is_in_virtualenv is worth a second look before the data is relied upon for analysis.

Important Files Changed

Filename	Overview
reflex/utils/telemetry.py	Adds is_in_virtualenv() and get_init_environment(); conda environments (CONDA_PREFIX) are not detected by is_in_virtualenv(), so conda users will always report in_virtualenv: false.
reflex/utils/templates.py	Correctly captures init_environment before scaffolding and passes it to telemetry.send; the placement is correct and the send call matches the existing signature.
tests/units/test_telemetry.py	Well-structured fixtures and tests cover PEP-405 venv detection, VIRTUAL_ENV fallback, system Python, pyproject.toml presence, requirements.txt presence, and empty directory.

Sequence Diagram

sequenceDiagram
    participant User
    participant initialize_app
    participant get_init_environment
    participant Filesystem
    participant telemetry_send

    User->>initialize_app: reflex init
    initialize_app->>initialize_app: check Config.FILE exists (reinit guard)
    initialize_app->>get_init_environment: capture pre-scaffolding state
    get_init_environment->>get_init_environment: is_in_virtualenv() [sys.prefix, VIRTUAL_ENV]
    get_init_environment->>Filesystem: Path("pyproject.toml").exists()
    get_init_environment->>Filesystem: Path("requirements.txt").exists()
    get_init_environment-->>initialize_app: "{in_virtualenv, has_pyproject_toml, has_requirements_txt}"
    initialize_app->>initialize_app: scaffold template
    initialize_app->>telemetry_send: "send("init", template=…, properties=init_environment)"
    telemetry_send-->>User: async fire-and-forget to PostHog

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_{Reviews (2): Last reviewed commit: "Merge remote-tracking branch 'upstream/m..." | Re-trigger Greptile}

[codspeed-hq]

Merging this PR will not alter performance

✅ 24 untouched benchmarks

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_{Comparing FarhanAliRaza:init-even-venv (adecb73) with main (447db31)}

[masenf]

@greptile

[masenf]

add has_uv_lock and has_reflex_lock (directory) here

[masenf]

short circuit when telemetry is not enabled

[masenf]

move this call above the constants.Config.FILE.exists() check and also include this information in the reinit event