Diff

mxcli provides two diff commands for comparing MDL scripts against project state and viewing local changes in MPR v2 projects.

mxcli diff

Shows what mxcli exec would change in the project if it ran the script, without changing the project.

Usage:

mxcli diff -p app.mpr changes.mdl

How it works: diff runs exec

diff copies the project to a scratch folder, runs the script there with exec’s own code — the same pre-flight checks, the statements in order, under the script’s language header — and then compares the copy with the project unit by unit. What it reports is therefore exactly what exec would write: there is no second judgement to disagree with exec’s. The project itself is only read, and the scratch copy is deleted afterwards (it leaves out .git, deployment, releases and node_modules).

Each unit exec would add, rewrite, move or remove is shown as the describe of the document before and after. A domain model is shown per entity and association, module security per module role, and project security per user role and demo user. This covers every document kind — pages, snippets, layouts, navigation, settings, security, folders — and statements of every kind, including grant, alter, move and drop.

--- Page.MyFirstModule.Home_Web (current)
+++ Page.MyFirstModule.Home_Web (script)
@@ -1,6 +1,6 @@
 create or modify page MyFirstModule.Home_Web (
   Title: 'Homepage',
-  Layout: Atlas_Core.Atlas_TopBar,
+  Layout: Atlas_Core.Atlas_Default,
   PopupResizable: true
 ) {

Summary: 0 new, 1 modified, 0 removed — exec would write 1 unit(s)

A unit exec rewrites although its description does not change — a property describe does not print, a translation, a move to another folder — is listed on one line with what changes, so a write is never hidden behind identical MDL:

Modified: Page MyFirstModule.Home_Web: changed: CanvasHeight, CanvasWidth
Modified: Microflow Shop.ACT_Apply: moved to 'Shop/Archive'

Files exec writes next to the model (Java sources, theme files) are listed as New file: / Modified file:.

What diff no longer reports

Because the verdict is exec’s own, a script exec has already applied diffs as exec would write nothing. Before (ako/mxcli#907), diff compared the script’s text with the stored document’s description and reported phantom changes exec never makes — Boolean against the stored Boolean default false, String against String(unlimited), a position, a re-laid-out flow — and did not compare pages, translations or layouts at all.

Refusals and errors

• A script exec’s pre-flight refuses (a check error, an unresolved reference, a name clash) is reported as Refused, with the same report exec prints, and nothing is written. --no-check skips the pre-flight, as it does for exec.
• A statement exec stops at — a plain create of a document that exists (ako/mxcli#807), a create or modify of a flow the splice cannot make under mdl 1; — is reported as Refused with exec’s error, after the changes exec makes before it. --continue-on-error runs every statement, as it does for exec.
• Statements that depend on earlier ones (a flow calling a microflow the script creates first) are diffed like any other, because the earlier ones run first (ako/mxcli#856).

Refused: exec would stop at this error, having written nothing: entity already exists: Shop.Order — …

Summary: 0 new, 0 modified, 0 removed — exec would write nothing

diff always runs the script with the file engine on the scratch copy, also under --mcp: the script is executed for real, and only the copy may receive it. --exec-output prints what exec reports while it runs.

For the same reason a script may not reach past the copy. A connect to the -p project (a headerless script may hold one, and so may a script it runs with execute script) is followed on the copy; a connect to any other project, a sql <alias> <query> and an import from are refused with an error, because diff has no copy of that project or database and does not run them for real.

mxcli diff-local

Compares local changes against a git reference for MPR v2 projects. MPR v2 (Mendix >= 10.18) stores documents as individual files in an mprcontents/ folder, making git diff feasible.

Usage:

# Compare against HEAD (latest commit)
mxcli diff-local -p app.mpr --ref HEAD

# Compare against a specific commit
mxcli diff-local -p app.mpr --ref HEAD~1

# Compare against a branch
mxcli diff-local -p app.mpr --ref main

# Compare two arbitrary revisions (git range syntax)
mxcli diff-local -p app.mpr --ref main..feature-branch

# Three-dot range (changes since common ancestor)
mxcli diff-local -p app.mpr --ref main...feature-branch

MPR v2 Requirement

diff-local only works with MPR v2 format (Mendix >= 10.18), where documents are stored as individual files. MPR v1 projects store everything in a single SQLite database, making file-level git diff impractical.

Workflow

Review Before Applying

# 1. Generate MDL changes
# (AI assistant creates changes.mdl)

# 2. Review what would change
mxcli diff -p app.mpr changes.mdl

# 3. If satisfied, apply
mxcli exec changes.mdl -p app.mpr

Track Changes Over Time

# After making changes, see what changed since last commit
mxcli diff-local -p app.mpr --ref HEAD

# See changes since two commits ago
mxcli diff-local -p app.mpr --ref HEAD~2

Compare Branches

# What changed between main and your feature branch
mxcli diff-local -p app.mpr --ref main..feature-branch

# Feed diff into an LLM for review
mxcli diff-local -p app.mpr --ref main..feature-branch > changes.diff