Dry Run & Diff

Dry Run

With --dry-run, nothing is written, committed, or pushed. Loom just shows you what would happen.

loom run ./onboard-service \
  -p serviceName=payments \
  --dry-run

All operations are simulated:

• newFiles logs which files would be written and their sizes
• patch logs which files would be patched
• shell logs the command that would run
• commitPush logs the commit message
• pr logs the PR title

Diff

To see the actual rendered file contents and patch results as a colored unified diff, use the loom diff command. Add --quick for a fast, no-execution preview equivalent to a dry-run:

loom diff ./onboard-service \
  -p serviceName=payments \
  --quick

--quick simulates the run -- no files are written and nothing executes.

Example output

For a new file:

--- /dev/null
+++ src/INTEGRATIONDEVOPS-NPRD/test.loom.yaml
@@ -0,0 +1,7 @@
+version: v1
+spec:
+  certificate_authority:
+    name: Let's Encrypt
+  domains:
+  - test.loom

For a patched file:

--- config/my-config.yaml
+++ config/my-config.yaml
@@ -2,6 +2,9 @@
 kind: ConfigMap
 metadata:
   name: my-config
+  labels:
+    added-by: loom
 data:
   key: value
+  newKey: newValue

The diff output is colored in terminals: green for additions, red for removals, cyan for headers.

Combining with Local Run

Full loom diff (without --quick) already runs the module in local mode and prints a real git diff — including changes made by shell commands, which the dry-run preview cannot show. Add --target-path to keep the clones in numbered subdirectories you can inspect afterwards:

loom diff ./onboard-service \
  -p serviceName=payments \
  --target-path ./preview

For modules without a target spec, --target-path is used directly as the target directory.

TIP

--dry-run takes precedence over --local-run. If both are set, dry-run wins and nothing is written.