# Dry-Run Mode

Preview what jbundle will do without executing anything.

## Usage

```bash
jbundle build --input ./my-app --output ./dist/app --dry-run
```

## What It Shows

```
[dry-run] Build plan for ./my-app → ./dist/app

  Build system:  DepsEdn (clojure -T:build uber)
  Target:        Target { os: Linux, arch: X86_64 }
  JDK version:   21
  JDK source:    cached ✓
  Modules:       auto-detect (jdeps)
  Runtime:       create via jlink
  Profile:       cli
  Shrink:        enabled
  AppCDS:        enabled
  CRaC:          disabled
  JVM args:      -Xmx512m

  No actions taken.
```

| Field                     | Description                                                         |
| ------------------------- | ------------------------------------------------------------------- |
| **Build system**          | Detected build tool and command that would run                      |
| **Target**                | OS and architecture of the output binary                            |
| **Cross-compile**         | Shown when target differs from host platform                        |
| **JDK version**           | Which JDK version will be used                                      |
| **JDK source**            | Whether the JDK is cached, local (`--java-home`), or needs download |
| **Modules**               | Auto-detect via jdeps or manual override                            |
| **Runtime**               | New via jlink or reusing existing (`--jlink-runtime`)               |
| **Profile**               | `cli` (fast startup) or `server` (throughput)                       |
| **Shrink/AppCDS/CRaC**    | Feature toggles                                                     |
| **JVM args / Build args** | Extra arguments, if any                                             |

## When to Use

**Validating config before a long build:**

```bash
# Check that jbundle.toml is picking up the right settings
jbundle build --input . --output ./app --dry-run
```

**Verifying cross-compilation setup:**

```bash
# Confirm host + target JDK strategy
jbundle build --input . --output ./app --target linux-x64 --dry-run
```

**Debugging CI:**

```bash
# Add to your CI pipeline before the real build
jbundle build --input . --output ./dist/app --dry-run
jbundle build --input . --output ./dist/app
```

**Checking build system detection:**

```bash
# Repos with multiple build files (deps.edn + project.clj)
jbundle build --input ./my-project --output ./app --dry-run
```

## Configuration

Dry-run is CLI-only — there's no `jbundle.toml` equivalent. All other config options (`--java-version`, `--profile`, `--target`, etc.) work normally with `--dry-run` to preview their effect.


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