Remove R/rpy2 dependency; replace with cffdrs_py by conbrad · Pull Request #5176 · bcgov/wps

conbrad · 2026-03-02T21:52:55Z

Replaces all R/rpy2 calls in app/fire_behaviour/cffdrs.py with the pure-Python cffdrs_py package, eliminating the R runtime as a dependency.

Changes:

Rewrote all FWI and FBP wrappers in cffdrs.py to use cffdrs_py submodule imports
Removed CFFDRS singleton, r_importer.py, and CFFDRS pre-warming from startup
Removed rpy2 from pyproject.toml; added cffdrs git dependency (pinned to commit)
Removed R installation from base image Dockerfile, OpenShift build.yaml, and local dev Dockerfile
Improved None guards on bui_calc, initial_spread_index, fire_weather_index, and crown_fraction_burned; fixed drought_code silently substituting rh=0 when RH is None; fixed
length_to_breadth_ratio returning rather than raising CFFDRSException; added per-row error handling to hourly_fine_fuel_moisture_code
Updated 32 fba_calc tests (removed CFFDRS.instance() pre-warming); deleted test_r.py

Behavioural notes:

duff_moisture_code returns 0.0 (not ~0.256) when temperature < 1.1°C — cffdrs_py clamps temp to -1.1 before computing the drying rate (Eq. 16), zeroing it out. The R implementation did not apply this clamp.
cbh uses a fuel type default if it is None, this was handled internally before in the R library.

Closes #1926

Test Links:
Landing Page
MoreCast
Percentile Calculator
C-Haines
FireCalc
FireCalc bookmark
Auto Spatial Advisory (ASA)
HFI Calculator
SFMS Insights
Fire Watch

backend/packages/wps-api/src/app/fire_behaviour/cffdrs.py

codecov · 2026-03-02T21:59:11Z

Codecov Report

❌ Patch coverage is 74.07407% with 35 lines in your changes missing coverage. Please review.
✅ Project coverage is 69.06%. Comparing base (8231082) to head (c9c728a).
⚠️ Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
.../packages/wps-api/src/app/fire_behaviour/cffdrs.py	73.01%	20 Missing and 14 partials ⚠️
...pi/src/app/auto_spatial_advisory/critical_hours.py	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5176      +/-   ##
==========================================
- Coverage   69.06%   69.06%   -0.01%     
==========================================
  Files         394      393       -1     
  Lines       16418    16337      -81     
  Branches     1846     1820      -26     
==========================================
- Hits        11339    11283      -56     
+ Misses       4495     4479      -16     
+ Partials      584      575       -9

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backend/packages/wps-api/src/app/fire_behaviour/cffdrs.py

brettedw · 2026-03-05T21:18:58Z

cbh uses a fuel type default if it is None, this was handled internally before in the R library.

Where does this happen? I think cffdrs_py still handles it internally

backend/packages/wps-api/src/app/fire_behaviour/cffdrs.py

conbrad · 2026-03-05T22:55:36Z

cbh uses a fuel type default if it is None, this was handled internally before in the R library.

Where does this happen? I think cffdrs_py still handles it internally

backend/packages/wps-api/src/app/routers/fba_calc.py

brettedw · 2026-03-06T00:22:44Z

cbh uses a fuel type default if it is None, this was handled internally before in the R library.

Where does this happen? I think cffdrs_py still handles it internally

backend/packages/wps-api/src/app/routers/fba_calc.py

Took me awhile to figure out what was happening here, I was confused because R doesn't have fuel type default handling in those functions either, but it comes down to Python vs R math operations on NULL/None. Python will error, R won't.

Non-C6 fuel: ROS still comes from RSS (rate_of_spread.r (line 173)), so you often still get a numeric ROS.
C6 fuel: ROS depends on CFB/RSO, so it typically becomes NA (rate_of_spread.r (line 174)).

This is why C6 fuel type has built in 2 and 7m CBH on the front end

Regardless, all the calculations in FireCalc look the same to me

dgboss

🚀 So nice to finally remove R! We've been talking about this since I joined the team I think.

brettedw · 2026-03-10T20:03:36Z

Do you think we should remove R installation and setup from mac.sh and put it elsewhere? It's not necessary for local running and builds anymore, but still nice to have it installed as a dev for comparing R to Python CFFDRS

sonarqubecloud · 2026-03-10T20:59:37Z

Quality Gate passed

Issues
3 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

conbrad · 2026-03-10T21:06:34Z

remove R install from mac setup

Done in: c9c728a

brettedw · 2026-03-10T21:25:14Z

backend/packages/wps-api/src/app/routers/fba_calc.py

-        crown_base_height=requested_station.crown_base_height,
+        crown_base_height=requested_station.crown_base_height
+        if requested_station.crown_base_height is not None
+        else FUEL_TYPE_DEFAULTS[requested_station.fuel_type]["CBH"],


cffdrs_py has crown_base_height and crown_fuel_load. Wondering if we should start using those vs our FUEL_TYPE_DEFAULTS. Or if that's a later ticket. PC, PDF and CC might be harder to sort out

Yeah let's do a follow up if we didn't use that before from the R package.

brettedw

Awesome, thank you!

conbrad added 9 commits March 2, 2026 13:35

switch to cffdrs py

b969dfb

delete r reference raise CFFDRS exception

c760897

fix rh check

c214128

better error case handling

f7aeeb3

improve guard checks

a0b162f

improve cfb guards

f3c7af0

clamping comment

148b129

add boundary tests

1581c70

drop r from base image

896c86d

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conbrad added 3 commits March 2, 2026 14:31

keep behaviour

82dfd11

validate cbh

118be4f

use fuel type defaults for cbh

cbee151

conbrad requested review from brettedw and dgboss March 2, 2026 22:45

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conbrad added 2 commits March 3, 2026 17:14

Merge branch 'main' into task/cffdrs-py-no-r

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Formatting

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conbrad added 2 commits March 9, 2026 16:53

remove comment

74fbd6f

remove hffmc

f6b0de4

conbrad added 5 commits March 9, 2026 17:08

fix cfb for c6

95847c0

throw if wsv is none

4d37183

remove unused function

cf41aa3

input guards

ee36112

Merge branch 'main' into task/cffdrs-py-no-r

ccd5e70

conbrad requested review from brettedw and dgboss March 10, 2026 00:35

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conbrad added 3 commits March 10, 2026 13:40

Merge branch 'main' into task/cffdrs-py-no-r

28dbcdf

cfb test changes for c6

7a9463b

remove R install from mac setup

c9c728a

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conbrad requested a review from brettedw March 10, 2026 21:26

brettedw approved these changes Mar 10, 2026

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conbrad temporarily deployed to production March 10, 2026 21:31 Inactive

conbrad merged commit 65ad04a into main Mar 10, 2026
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conbrad deleted the task/cffdrs-py-no-r branch March 10, 2026 21:41

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