GUIDE

The Complete Guide to Dependency Mapping

Dependencies define how software actually works. This guide covers everything: types, mapping techniques, visualization, impact analysis, and practical applications.

[IMAGE: Rich dependency graph showing different connection types—calls, imports, inheritance—with nodes colored by type and edges showing flow direction]

Key Insight: You can't safely change code you don't understand. You can't understand code without understanding its dependencies.

What Are Dependencies?

A dependency exists whenever one piece of code relies on another. When function A calls function B, A depends on B. Dependencies are the invisible threads that hold software together—and the threads that cause unexpected breaks.

Types of Dependencies

Call Dependencies

A() { B(); }

Function A calls function B. Most common type. When B's signature changes, A may break.

Import Dependencies

import { x } from './Y'

File X imports from file Y. Changes to what Y exports affect X.

Inheritance Dependencies

class Child extends Parent

Child depends on Parent's structure. Changes cascade down.

Interface Dependencies

Class implements interface. Interface changes require class updates.

Data Dependencies

Function A produces data that function B consumes. Requires data flow analysis.

Package Dependencies

Your code depends on external libraries. Version changes can break everything.

Direct vs Transitive Dependencies

Direct: A directly calls B. You can see this in A's code.

Transitive: A calls B, B calls C. A transitively depends on C, even though A never mentions C. Change C, and A might break.

Most dependency surprises come from transitive dependencies. You change something "isolated" and something "unrelated" breaks. It wasn't unrelated—you just didn't see the chain.

[IMAGE: Chain showing A→B→C with transitive dependency line A→C drawn as dashed, showing the hidden relationship]

Dependency-Based Impact Analysis

The primary practical use: answering "what breaks if I change this?"

Identify the Change Point. What element are you modifying?

Find Direct Dependents. What directly depends on this? These need review.

Trace Transitive Dependents. Follow the chain outward.

Assess Impact. How many affected? How critical? This is your blast radius.

Good dependency tools automate this. One click shows the entire impact radius.

Dependency Problems to Watch For

Circular Dependencies

A depends on B depends on C depends on A. Creates tight coupling, build issues, testing nightmares. Break the cycle.

God Objects

One element that everything depends on. Change it, break everything. Refactor into smaller pieces.

Hidden Dependencies

Dependencies not visible in code: shared state, configuration, environment. Document or eliminate.

Unused Dependencies

Code nobody calls. Dead weight that still needs maintenance. Identify and delete it.

[IMAGE: Dependency graph with orphaned nodes highlighted—dead code visually obvious at the edges]

Dependency Best Practices

Keep dependencies visible

Prefer explicit imports over global access. Visible dependencies are manageable dependencies.

Minimize transitive chains

Shorter chains mean less surprise propagation. Flatten where possible.

Watch dependency count

An element with 50 dependents needs careful handling. High-impact changes require high care.

Layer your architecture

Dependencies should flow in one direction. Layered architecture prevents circular messes.

Review dependency changes

New dependencies in PRs deserve discussion. They shape future architecture.

Regularly audit

Run dependency analysis periodically. Catch problems before they compound.

Map Your Dependencies

LOOM maps every dependency in your codebase. See the connections. Understand the impact. Code with confidence.

Try LOOM Explore Dependency Mapping

Free tier available. No credit card required.