Rename internal Fusion parser naming to v2

[aiguofer]

Summary

• Rename internal Fusion parser naming to v2 as part of the broader Fusion to v2 rebrand: exception classes (FusionParserError, FusionParserSchemaError, FusionParserVersionError to V2ParserError, V2ParserSchemaError, V2ParserVersionError), the core/dbt/parser/fusion.py module (to v2.py, with parse_with_fusion to parse_with_v2 and related private helpers), config/utils.py helper names, and the FUSION_PARITY_GET_NODES_PLUGINS constant in parser/manifest.py.
• Reword user-facing help text, error messages, log strings, and comments from Fusion to v2, and rename corresponding test files, classes, and fixtures, including the fusion_warn_error_options.py module and its FUSION_WARN_ERROR_OPTION_NAMES constant (renamed to v2_warn_error_options.py / V2_WARN_ERROR_OPTION_NAMES).
• Leave the "UnsupportedFusionFeature" string value inside that constant untouched, since it mirrors an error code name that has not been renamed in the upstream v2 engine yet; the surrounding module/constant names are our own internal naming and were renamed along with everything else.

No user-facing behavior change; this is purely an internal naming and copy update.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.56%. Comparing base (37c0ef1) to head (3709d5b).

Additional details and impacted files

@@             Coverage Diff              @@
##           1.latest   #16281      +/-   ##
============================================
- Coverage     91.57%   91.56%   -0.02%     
============================================
  Files           223      223              
  Lines         28346    28346              
============================================
- Hits          25959    25956       -3     
- Misses         2387     2390       +3     

Flag	Coverage Δ
integration	87.79% <85.29%> (-0.02%)	⬇️
unit	67.05% <100.00%> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Components	Coverage Δ
Unit Tests	67.05% <100.00%> (ø)
Integration Tests	87.79% <85.29%> (-0.02%)	⬇️

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[Copilot]

🟡 Changes recommended

It introduces potentially breaking public exception renames and a few remaining Fusion-branded identifiers/docstrings that should be made consistent (or aliased) to match the PR’s “no behavior change” claim.

Once you've addressed the issues Copilot identified, you can request another Copilot review.

Pull request overview

This PR completes an internal terminology rebrand from “Fusion” to “v2” across the external v2 parser integration in dbt-core, including exception types, parser module naming, CLI/help text, and associated unit/functional tests. The intent is to keep behavior the same while aligning internal naming and copy with the “v2” branding.

Changes:

• Renamed the external-parser integration surface from fusion to v2 (module/function names and exception classes), and updated CLI help/error strings accordingly.
• Updated unit + functional tests and parity tooling docs/plugins to reflect the v2 naming.
• Updated warn/error options filtering copy to describe “v2 engine” names while keeping the vendored constant set intact.

File summaries

File	Description
tests/unit/parser/test_v2.py	Updates unit tests to import/use dbt.parser.v2 and V2Parser* exceptions.
tests/unit/config/test_v2_warn_error_options.py	Renames test constants/messages from Fusion to v2 and updates emitted Note copy.
tests/unit/cli/test_setup_manifest.py	Updates CLI manifest setup tests to assert the v2 parser branch calls parse_with_v2.
tests/unit/cli/test_flags.py	Renames the flag test class to v2 naming.
tests/unit/artifacts/test_test_node_discrimination.py	Updates commentary to refer to the v2 parser branch.
tests/functional/v2_parser/test_v2_parser_branch.py	Renames the end-to-end “fusion parser branch” tests to the v2 naming.
tests/functional/v2_parser/init.py	Ensures v2_parser functional test package is present/importable.
tests/functional/v2_parser_parity/v2_self_parser.py	Updates the v2-self shim to patch dbt.parser.v2._run_v2 and related copy.
tests/functional/v2_parser_parity/README.md	Updates parity plugin documentation to reference parse_with_v2 and v2 naming.
tests/functional/v2_parser_parity/plugin.py	Updates CLI help text for the parity plugin to describe routing the v2 parser subprocess.
tests/functional/configs/test_warn_error_options.py	Renames functional tests to describe v2-only warn/error options tolerance.
core/dbt/tests/util.py	Updates comments describing the v2 parser flow fallback behavior for get_manifest().
core/dbt/parser/v2.py	Renames the integration module and internal APIs/messages from Fusion to v2.
core/dbt/parser/manifest.py	Updates plugin-guard comments/docstrings to reference v2 parser mode.
core/dbt/jsonschemas/jsonschemas.py	Updates comment text referencing schemas “from the v2 parser”.
core/dbt/exceptions.py	Renames Fusion parser exception classes to V2Parser*.
core/dbt/deps/private_package.py	Updates docstring text to refer to the v2 engine.
core/dbt/config/utils.py	Renames internal variables for warn/error options partitioning to v2 naming; updates Note copy.
core/dbt/cli/requires.py	Switches setup_manifest() to import/call parse_with_v2 when USE_V2_PARSER is set.
core/dbt/cli/params.py	Updates CLI help strings to say “v2 parser” instead of “fusion parser”.
.changes/unreleased/Under the Hood-20260910-120000.yaml	Adds an “Under the Hood” changelog entry describing the naming rebrand.

Review details

Suppressed comments (3)

tests/unit/config/test_v2_warn_error_options.py:126

• This test class name still uses Fusion branding even though the docstring and the rest of the file have been renamed to v2. Renaming the class improves consistency and makes grepping for Fusion leftovers more reliable.
  core/dbt/parser/v2.py:329
• This docstring still refers to the subprocess as "fs" in multiple places, which is inconsistent with the v2 naming used elsewhere in this module and the CLI help/error strings. Updating the wording to "v2 parser" (or "v2 engine") would make it clearer for maintainers.
  core/dbt/parser/v2.py:296
• The comment above this block refers to "fs telemetry"; after the Fusion -> v2 rename it would be clearer/consistent to refer to the v2 parser (or v2 engine) telemetry.

• Files reviewed: 20/21 changed files
• Comments generated: 2
• Review effort level: Lite

---

💡 Add a code-review agent skill or configure MCP servers for context-aware, tailored reviews. Learn more in the docs.