tmdl-review

name	tmdl-review
description	Review a TMDL semantic-model diff for breaking schema changes before merging a PBIP change. Compares two versions of the *.tmdl files (a PR, or two git refs) and classifies every change as BREAKING / WARNING / INFO. Use when the user wants to know whether a Power BI / Fabric model change is safe to merge. Triggers — "revisa el diff TMDL", "breaking changes del modelo", "compara el modelo semántico", "¿este cambio rompe el modelo?", "review the TMDL diff", "detect breaking schema changes".
user-invocable	false

tmdl-review — detect breaking semantic-model changes

PBIP repos store the Power BI / Fabric semantic model as TMDL (*.tmdl) text files. A diff over those files is hard to read by eye: a dropped column, a changed dataType, or a deleted measure will break downstream reports, DAX, and refreshes, but looks the same in raw text as a harmless display-folder rename.

scripts/Tmdl-DiffReview.ps1 parses the model before/after a change and classifies every schema change by severity.

When to use

• A PR edits *.tmdl and you need to know whether it is safe to merge.
• Before opening a PR, to self-check your own model change.
• As part of /board work step 5 — Board-ReviewGate.ps1 runs this automatically when the PR touches *.tmdl (warn-only; it does not change the gate verdict).

Two modes

PR mode (no local clone needed) — reads the PR's changed *.tmdl via the GitHub API, fetching base and head content by ref:

$env:GH_TOKEN = [Environment]::GetEnvironmentVariable('GITHUB_TOKEN_PERSONAL','User')
.\scripts\Tmdl-DiffReview.ps1 -Repo <owner/name> -PR <n>

Local mode — diffs *.tmdl with git in the current working copy:

.\scripts\Tmdl-DiffReview.ps1 -Base main -Head HEAD

Severity rules

Severity	Change
BREAKING	table / column / measure / hierarchy / relationship / role deleted; column dataType changed; column sourceColumn changed; column/measure renamed
WARNING	measure / partition-source expression changed; column summarizeBy changed; object becomes hidden; relationship crossFilteringBehavior changed
INFO	any addition; formatString / displayFolder / description / lineageTag changes

A delete + add of the same kind under the same parent, with identical signature (column dataType+sourceColumn, or measure expression), is reported as RENAMED (breaking — references by name break) rather than an unrelated pair.

Flags

• -FailOnBreaking — exit 1 when any BREAKING change is found (default: warn only, exit 0). The M3.3 hard merge-block uses this: Board-ReviewGate.ps1 runs the TMDL review with -FailOnBreaking (alongside Bpa-GateReview.ps1 -FailOn error) and blocks the merge when either finds a problem in a PR that touches the model (#16).
• -Json — emit the findings object as JSON instead of the colored report.

Limits (v1, honest)

• The comparison is per file: only changed *.tmdl are compared. A cross-file effect (a relationship in an unchanged file referencing a column dropped in a changed file) is caught only if both files changed.
• The parser is pragmatic and line-based (indentation), not a full TMDL grammar. Calculation groups, perspectives, translations, and role filter expressions are not diffed in detail. Table/column/measure/hierarchy/partition/relationship/role existence and the key breaking properties are covered.