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The inspect command prints a hierarchical tree representation of the contents of a Dart kernel (.dill) file. Use it to verify obfuscation results, debug compilation issues, or explore the structure of compiled Dart code.

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Usage

refractor inspect [options] <path.dill>
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path.dill
string
required
Path to the .dill file to inspect. This is a positional argument (not a flag).

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Options

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--sdk
boolean
default:"false"
Include dart:* SDK libraries in the output. By default, only user code is shown.

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Output Format

The inspect command displays a tree structure showing:
  • Libraries - Top-level modules and packages
  • Classes - Type definitions and their members
  • Procedures - Functions and methods
  • Fields - Class properties and variables

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Example Output

Inspecting an obfuscated kernel file: 
refractor inspect build/out.dill

📦 file:///Users/dev/myapp/lib/main.dart
  └─ class A
      ├─ field B: String
      ├─ constructor A()
      └─ method C() → void
  └─ procedure D() → void

📦 package:myapp/utils.dart
  └─ class E
      └─ method F() → int
Notice the short, meaningless names (A, B, C, etc.) - this indicates the rename pass successfully obfuscated the original identifiers.

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With SDK Libraries

Include Dart’s core libraries in the output: 
refractor inspect --sdk build/out.dill

📦 dart:core
  └─ class Object
      ├─ method toString() → String
      ├─ method hashCode → int
      └─ ...
  └─ class String
      └─ ...

📦 dart:async
  └─ class Future
      └─ ...

📦 file:///Users/dev/myapp/lib/main.dart
  └─ class A
      └─ ...
The --sdk flag produces very verbose output since Dart’s SDK contains hundreds of classes and functions. Use it only when debugging SDK-related issues.

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Use Cases

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Verify Obfuscation

Check that your code was properly obfuscated: 
refractor inspect original.dill

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Debug Compilation Issues

If your build fails after obfuscation, inspect the kernel file to identify problematic transformations: 
refractor build --target kernel
refractor inspect build/out.dill

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Compare Original vs Obfuscated

Generate a non-obfuscated kernel file for comparison: 
# Create unobfuscated kernel
dart compile kernel lib/main.dart -o build/original.dill

# Create obfuscated kernel
refractor build --target kernel

# Compare structures
refractor inspect build/original.dill > original.txt
refractor inspect build/out.dill > obfuscated.txt
diff original.txt obfuscated.txt
Use the symbol map (generated during build) to reverse-lookup obfuscated names back to their originals when debugging.

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Analyze Third-Party Packages

Inspect any .dill file, including compiled packages: 
refractor inspect ~/.pub-cache/hosted/pub.dev/package_name-1.0.0/lib/package.dill

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Tree Structure Reference

The output tree uses these symbols:
  • 📦 - Library or package
  • └─ - Last item in a group
  • ├─ - Item with siblings below
  • class - Type definition
  • field - Member variable
  • constructor - Constructor method
  • method - Instance or static method
  • procedure - Top-level function
The tree format is designed for human readability. For programmatic analysis, consider using the Dart kernel API directly.

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Technical Details

The inspect command:
  1. Loads the .dill file using FileKernelIO().load()
  2. Parses the kernel component structure with KernelParser()
  3. Filters out SDK libraries unless --sdk is specified
  4. Renders a hierarchical tree with KernelTreePrinter()
The output includes all kernel entities visible in the component’s library scope.

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Examples

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Inspect Build Output

refractor build --target kernel
refractor inspect build/out.dill

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Check Specific Library

Build a kernel file and verify a specific library was obfuscated: 
refractor inspect build/out.dill | grep "package:myapp"

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Save Output for Analysis

refractor inspect build/out.dill > kernel-structure.txt

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Compare Before and After

# Generate both versions
dart compile kernel lib/main.dart -o before.dill
refractor build --target kernel --output after

# Inspect both
refractor inspect before.dill
refractor inspect after/out.dill

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Common Issues

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Missing Argument Error

If you see: 
Missing required argument: <path.dill>
Make sure you provide the path to a .dill file: 
refractor inspect build/out.dill

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File Not Found

If the .dill file doesn’t exist: 
Error: Cannot open file: build/out.dill
Ensure you’ve run refractor build --target kernel first, or provide the correct path.

refractor build

Generate .dill files to inspect

Understanding Obfuscation

Learn how Refractor transforms your code

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