From 43a5352c9b007f3620c011f95c2a4b2540c504eb Mon Sep 17 00:00:00 2001
From: "Sam S. Yu" <25761223+yudataguy@users.noreply.github.com>
Date: Tue, 4 Aug 2026 20:16:47 -0700
Subject: [PATCH] fix(build): pin pre-commit's Python to .python-version

pre-commit builds its hook environments with whatever interpreter happens
to run it. Nothing pinned that, so on a machine where uvx resolved an
older Python the hooks were built against it, and `make fmt` failed with
a SyntaxError that has nothing to do with the caller's changes:

    File "<unknown>", line 195
        assert updated_time > initial_time, f"Time should increase. Initial: {
    SyntaxError: unterminated string literal

rtc_test.py:195 uses a multi-line f-string, which is valid under the
project's declared Python (3.13, PEP 701) but not under 3.11, so the
interrogate hook could not parse it. CI happens to resolve a new enough
interpreter, so this only bites locally and only on some machines.

Pin the interpreter for uvx-run tooling to .python-version, keeping one
source of truth. uv downloads the pinned interpreter when it is missing,
so this needs no setup from contributors.

Verified with a cleared pre-commit cache: `make fmt` rebuilds every hook
environment and all hooks pass.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_011kehXMi9zAAoPJ3PgfRd81
---
 Makefile               | 4 ++--
 makelib/build-tools.mk | 9 +++++++++
 2 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/Makefile b/Makefile
index af982516..e9ed6dfe 100644
--- a/Makefile
+++ b/Makefile
@@ -58,11 +58,11 @@ zephyr-setup: fprime-venv ## Set up Zephyr environment
 
 .PHONY: pre-commit-install
 pre-commit-install: uv ## Install pre-commit hooks
-	@$(UVX) pre-commit install > /dev/null
+	@$(UVX_PINNED) pre-commit install > /dev/null
 
 .PHONY: fmt
 fmt: pre-commit-install ## Lint and format files
-	@$(UVX) pre-commit run --all-files
+	@$(UVX_PINNED) pre-commit run --all-files
 
 .PHONY: data-budget
 data-budget: fprime-venv ## Analyze telemetry data budget (use VERBOSE=1 for detailed output)
diff --git a/makelib/build-tools.mk b/makelib/build-tools.mk
index 9e346c8f..f2dfb4d1 100644
--- a/makelib/build-tools.mk
+++ b/makelib/build-tools.mk
@@ -10,10 +10,19 @@ $(TOOLS_DIR):
 ### Tool Versions
 UV_VERSION ?= 0.8.13
 
+### Python version used for tooling environments. Single source of truth is .python-version, so
+### that tools do not silently build against whichever interpreter happens to be on the machine.
+PYTHON_VERSION ?= $(shell cat .python-version)
+
 ### uv & uvx
 UV_DIR ?= $(TOOLS_DIR)/uv-$(UV_VERSION)
 UV ?= $(UV_DIR)/uv
 UVX ?= $(UV_DIR)/uvx
+### Pin the interpreter for uvx-run tooling. pre-commit builds its hook environments with whatever
+### Python runs it, so without this a machine defaulting to an older interpreter builds hook
+### environments that cannot parse project sources written for .python-version. uv downloads the
+### pinned interpreter if it is missing.
+UVX_PINNED ?= $(UVX) --python $(PYTHON_VERSION)
 .PHONY: uv
 uv: $(UV) ## Download uv
 $(UV): $(TOOLS_DIR)