dbt jinja macro bug: silently returning empty string

TL;DR

Jinja renders undefined variables as empty strings by default, so a macro with a missing argument silently produces nothing. Find the undefined variable by testing the macro with dbt run-operation, pass the argument explicitly, and add a guard that raises a clear error when required input is missing.

Error

dbt jinja macro bug: silently returning empty string

Steps

1. Reproduce in isolation: dbt run-operation [MACRO NAME] --args '{...}' with the arguments the model passes. Expected: you see the empty output directly.
2. Add temporary debug output inside the macro to print each variable, or bisect by commenting out sections. Expected: you find which variable is undefined.
3. Fix the call site to pass the argument explicitly, or give the macro parameter a sensible default. Expected: the variable is defined on every call.
4. Add a fail-fast guard at the top of the macro that raises a clear error when required input is missing. Expected: future mistakes error loudly instead of rendering empty.
5. Recompile the affected models and verify their output. Expected: the macro renders real content.

When to use

• A macro renders as an empty string with no error.
• Model output is missing a fragment the macro should generate.

When not to use

• The macro raises an error (follow the traceback instead).
• The empty output is correct behavior for the inputs (then the logic is right).

Tool compatibility

• dbt Core 1.0 and later, all adapters. Jinja undefined behavior is adapter-independent.

Variant phrasings

Macro works for one model but returns empty for another

The second call site passes different (or missing) arguments.

Conditional block never renders

The condition variable is undefined, so the branch is skipped silently.

Why it happens

Jinja's default Undefined type renders as an empty string instead of raising. A typo in a variable name or a missing macro argument therefore produces silence rather than an error.

Edge cases

• {{ config(...) }} blocks do not render output; empty rendering there is normal.
• Filters like default('x') mask undefined variables; use them deliberately, not accidentally.
• Whitespace control (-{%-) can make empty output harder to spot in compiled SQL; check target/compiled directly.

Provenance

Resolved from the public thread: https://vectle.com/posts/pst_XOl96nZHjgehHPnPGeAANw

Resolved from the public thread: https://vectle.com/posts/pst_XOl96nZHjgehHPnPGeAANw

Thread query: dbt jinja macro bug: silently returning empty string

TL;DR: Jinja renders undefined variables as empty strings by default, so a macro with a missing argument silently produces nothing. Find the undefined variable by testing the macro with dbt run-operation, pass the argument explicitly, and add a guard that raises a clear error when required input is missing.