## TL;DR

`dbt docs generate` crashed because the manifest or catalog data it read was malformed or missing, often from stale artifacts or a core/adapter version mismatch. Delete `target/`, run a fresh `dbt compile`, then regenerate docs. If it persists, align your adapter version with dbt-core.

## Error

```text
"dbt docs generate: 'NoneType' object is not iterable"
```

## Steps

1. Clear stale artifacts: delete the `target/` directory in the project. Expected: no old manifest.json or catalog.json remains.
2. Run a fresh `dbt compile` (or `dbt run` if you want catalog data from real relations). Expected: compilation succeeds and writes a fresh manifest.
3. Run `dbt docs generate`. Expected: it completes and writes catalog.json without the NoneType crash.
4. If it still crashes, check versions: `dbt --version` and confirm the adapter major version matches dbt-core. Expected: versions are aligned.
5. Serve and verify: `dbt docs serve`, then open the site and confirm models appear. Expected: the docs site renders with content.

## When to use

- `dbt docs generate` crashes with `'NoneType' object is not iterable`.
- The crash started after upgrading dbt or switching branches with different artifacts.

## When not to use

- Docs generate succeeds but catalog.json is empty (the adapter returned no metadata; check target and permissions).
- The docs site serves but is missing exposures or sources (a definition problem).

## Tool compatibility

- dbt Core 1.0 and later, all adapters. Artifact formats are adapter-independent.

## Variant phrasings

### docs generate crashes after a partial dbt run

A failed run leaves a partial manifest; clearing target and recompiling fixes it.

### 'NoneType' object has no attribute 'get' during docs generate

Sibling crash from the same family of malformed-artifact problems.

## Why it happens

Docs generation walks the manifest and the freshly queried catalog. A manifest from a different dbt version, or a catalog query that returned nothing where a list was expected, produces None where the code iterates.

## Edge cases

- Partial parsing can cache a broken manifest; `--no-partial-parse` on the recompile avoids reusing it.
- Custom `generate_docs` macros or docs blocks with bad YAML can also crash generation; check recently edited docs blocks.
- Very large projects can exhaust memory during generation; generate on a machine with headroom.

## Provenance

Resolved from the public thread: https://vectle.com/posts/pst_fH-ZSl4MvjQpZ2yDtZZZjw