Assess Impact

Understand the potential blast radius of changes before making them by analyzing dependencies, coupling patterns, and ownership.

Prerequisites

Omen CLI must be installed and available in PATH.

Workflow

Step 1: Check Symbol Blast Radius

Use the impact command to get transitive callers and callees in one call:

omen -f json impact <symbol-name> --depth 2

This returns affected files, caller/callee BFS levels, and the total count — much faster than building the picture manually.

To inspect a specific symbol first:

omen -f json symbol <symbol-name>

Step 2: Map File-Level Dependencies

Run the dependency graph analysis for file-level coupling:

omen -f json graph --compact

Identify:

Direct dependents (files that import the target)
Transitive dependents (files that import the dependents)

Step 3: Check Temporal Coupling

Run the temporal coupling analysis:

omen -f json temporal

Files with high temporal coupling to the target often need to change together even without explicit imports.

Step 3: Identify Stakeholders

Run the ownership analysis:

omen -f json ownership

Identify:

Primary owner of the target file
Owners of dependent files
Subject matter experts to consult

Impact Categories

Classify impact by type:

| Category | Description | Action | |----------|-------------|--------| | Direct | Explicit imports/calls | Will break if signature changes | | Implicit | Temporal coupling | May break due to shared assumptions | | Behavioral | Same owner/team | Likely understands the change | | Unknown | No coupling, different owner | Needs extra review |

Output Format

Present impact analysis as:

# Change Impact: `target/file.go:FunctionName`

## Direct Dependencies (will break)
- `consumer/a.go` - calls FunctionName directly
- `consumer/b.go` - uses returned type
- `test/target_test.go` - tests the function

## Implicit Dependencies (may break)
- `related/cache.go` - 0.85 temporal coupling
  - Always changes with target
  - Likely shares state or assumptions
- `related/config.go` - 0.72 temporal coupling
  - Often changes together
  - May depend on same configuration

## Stakeholders to Notify
- alice@example.com - Primary owner of target (85% of commits)
- bob@example.com - Owns consumer/a.go
- charlie@example.com - Owns related/cache.go

## Risk Assessment
- **Blast Radius**: 5 files directly, 12 files transitively
- **Coupling Risk**: 2 files with implicit dependencies
- **Team Impact**: 3 developers should be notified

## Recommended Approach
1. Coordinate with alice (primary owner)
2. Update tests in target_test.go first
3. Check related/cache.go for shared assumptions
4. Notify bob and charlie before merging

Reducing Impact

Strategies to minimize blast radius:

Add an adapter: Wrap changes behind a stable interface
Deprecate first: Add deprecation warnings before removing
Feature flag: Gate changes behind a flag for gradual rollout
Split the change: Break into smaller, reviewable pieces