Make the QA group scan the package extensions (#4860)

ExplicitImports reads the `[extensions]` table but skips any extension whose
module does not exist, and an extension module only exists once its trigger
package is loaded. The QA environment loaded no weakdeps, so none of the four
extensions were ever checked.

Add the weakdeps to `test/qa/Project.toml`, load them in `test/qa/qa.jl`, and
assert the extension modules actually exist -- ExplicitImports silently skips an
extension that fails to load, so a broken extension would otherwise drop coverage
to zero while QA stayed green.

Fix the findings this exposes in the extension sources:

* the three OrdinaryDiffEq precompile extensions relied on implicit imports from
  their trigger package and PrecompileTools;
* `MTKFMIExt` relied on implicit imports from SymbolicIndexingInterface and
  DocStringExtensions, and reached `setinput`, `setoutput`, `default_toterm` and
  `unwrap` through ModelingToolkit rather than through ModelingToolkitBase and
  SymbolicUtils which own them;
* `MTKFMIExt`'s `t`/`D` aliases move from a renaming import to `const`, since
  ExplicitImports tracks the pre-rename name and reports such an import as stale.

`FMIComponent`, `Base.RefValue` and the three ModelingToolkitBase metadata
helpers have no public spelling, so they are ignored with a comment naming the
owner.

Co-authored-by: ChrisRackauckas-Claude <accounts@chrisrackauckas.com>

Author: ChrisRackauckas-Claude

ext/MTKFMIExt.jl

@@ -1,13 +1,20 @@
 module MTKFMIExt
 
 using ModelingToolkit
-using SymbolicIndexingInterface
-using ModelingToolkit: t_nounits as t, D_nounits as D
-using DocStringExtensions
+using SymbolicIndexingInterface: NotSymbolic, symbolic_type
+using ModelingToolkitBase: t_nounits, D_nounits
+using DocStringExtensions: TYPEDEF, TYPEDFIELDS, TYPEDSIGNATURES
 import ModelingToolkit as MTK
+import ModelingToolkitBase as MTKBase
 import SciMLBase
+import SymbolicUtils
 import FMIImport as FMI
 
+# Spelled as `const` rather than `t_nounits as t`, because ExplicitImports reports a
+# renaming import as stale (it tracks the pre-rename name, which never appears in use).
+const t = t_nounits
+const D = D_nounits
+
 """
     $(TYPEDSIGNATURES)
 
@@ -173,7 +180,7 @@ function MTK.FMIComponent(
     inputs = []
     fmi_variables_to_mtk_variables!(
         fmu, FMI.getInputValueReferencesAndNames(fmu),
-        value_references, inputs, states, observed; postprocess_variable = v -> MTK.setinput(
+        value_references, inputs, states, observed; postprocess_variable = v -> MTKBase.setinput(
             v, true
         )
     )
@@ -187,7 +194,7 @@ function MTK.FMIComponent(
     outputs = []
     fmi_variables_to_mtk_variables!(
         fmu, FMI.getOutputValueReferencesAndNames(fmu),
-        value_references, outputs, states, observed; postprocess_variable = v -> MTK.setoutput(
+        value_references, outputs, states, observed; postprocess_variable = v -> MTKBase.setoutput(
             v, true
         )
     )
@@ -361,22 +368,22 @@ function fmi_variables_to_mtk_variables!(
         end
         if parameters
             vars = [
-                postprocess_variable(MTK.unwrap(only(@parameters $sname::stateT)))
+                postprocess_variable(SymbolicUtils.unwrap(only(@parameters $sname::stateT)))
                     for sname in snames
             ]
         else
             vars = [
-                postprocess_variable(MTK.unwrap(only(@variables $sname(t)::stateT)))
+                postprocess_variable(SymbolicUtils.unwrap(only(@variables $sname(t)::stateT)))
                     for sname in snames
             ]
         end
         for i in eachindex(vars)
             der = ders[i]
-            vars[i] = MTK.unwrap(vars[i])
+            vars[i] = SymbolicUtils.unwrap(vars[i])
             for j in 1:der
                 vars[i] = D(vars[i])
             end
-            vars[i] = MTK.default_toterm(vars[i])
+            vars[i] = MTKBase.default_toterm(vars[i])
         end
         for i in eachindex(vars)
             if i == 1

ext/MTKOrdinaryDiffEqBDFExt.jl

@@ -1,8 +1,8 @@
 module MTKOrdinaryDiffEqBDFExt
 
 using ModelingToolkit
-using OrdinaryDiffEqBDF
-using PrecompileTools
+using OrdinaryDiffEqBDF: FBDF
+using PrecompileTools: @compile_workload, @setup_workload
 using ModelingToolkit: t_nounits, D_nounits
 
 @setup_workload begin

ext/MTKOrdinaryDiffEqDefaultExt.jl

@@ -1,8 +1,8 @@
 module MTKOrdinaryDiffEqDefaultExt
 
 using ModelingToolkit
-using OrdinaryDiffEqDefault
-using PrecompileTools
+using OrdinaryDiffEqDefault: OrdinaryDiffEqDefault
+using PrecompileTools: @compile_workload, @setup_workload
 using ModelingToolkit: t_nounits, D_nounits
 
 @setup_workload begin

ext/MTKOrdinaryDiffEqRosenbrockExt.jl

@@ -1,8 +1,8 @@
 module MTKOrdinaryDiffEqRosenbrockExt
 
 using ModelingToolkit
-using OrdinaryDiffEqRosenbrock
-using PrecompileTools
+using OrdinaryDiffEqRosenbrock: Rodas5P
+using PrecompileTools: @compile_workload, @setup_workload
 using ModelingToolkit: t_nounits, D_nounits
 
 @setup_workload begin

test/qa/Project.toml

@@ -1,7 +1,11 @@
 [deps]
 Aqua = "4c88cf16-eb10-579e-8560-4a9242c79595"
+FMIImport = "9fcbc62e-52a0-44e9-a616-1359a0008194"
 JET = "c3a54625-cd67-489e-a8e7-0a5a0ff4e31b"
 ModelingToolkit = "961ee093-0014-501f-94e3-6117800e7a78"
+OrdinaryDiffEqBDF = "6ad6398a-0878-4a85-9266-38940aa047c8"
+OrdinaryDiffEqDefault = "50262376-6c5a-4cf5-baba-aaf4f84d72d7"
+OrdinaryDiffEqRosenbrock = "43230ef6-c299-4910-a778-202eb28ce4ce"
 SafeTestsets = "1bc83da4-3b8d-516f-aca4-4fe02f6d838f"
 SciMLTesting = "09d9d899-5365-40a9-917a-5f67fddea283"
 Test = "8dfed614-e22c-5e08-85e1-65c5234f0b40"
@@ -11,7 +15,11 @@ ModelingToolkit = {path = "../.."}
 
 [compat]
 Aqua = "0.8"
+FMIImport = "1"
 JET = "0.9,0.10,0.11"
+OrdinaryDiffEqBDF = "1, 2"
+OrdinaryDiffEqDefault = "1.2, 2"
+OrdinaryDiffEqRosenbrock = "1, 2"
 SafeTestsets = "0.1, 1"
 SciMLTesting = "1, 2.1"
 Test = "1"

test/qa/qa.jl

@@ -2,6 +2,29 @@ using ModelingToolkit
 using Aqua
 using JET
 using SciMLTesting
+using Test
+
+# ExplicitImports only sees an extension module once its trigger package is loaded, so
+# every weakdep is loaded here to bring the extensions into the checked module set.
+using FMIImport
+using OrdinaryDiffEqBDF
+using OrdinaryDiffEqDefault
+using OrdinaryDiffEqRosenbrock
+
+const MTK_EXTENSIONS = (
+    :MTKFMIExt,
+    :MTKOrdinaryDiffEqBDFExt,
+    :MTKOrdinaryDiffEqDefaultExt,
+    :MTKOrdinaryDiffEqRosenbrockExt,
+)
+
+# ExplicitImports silently skips an extension that fails to load, so assert the
+# extension modules actually exist rather than trusting a green run_qa.
+@testset "Extensions loaded" begin
+    for ext in MTK_EXTENSIONS
+        @test Base.get_extension(ModelingToolkit, ext) !== nothing
+    end
+end
 
 # Public names that reach ModelingToolkit's API surface only through
 # `@reexport using Symbolics` in ModelingToolkitBase. They are owned (and undocumented) by
@@ -18,11 +41,27 @@ const SYMBOLICS_OWNED_REEXPORTS = (
     :supremum,
 )
 
+# Names the extensions must reach for which no public spelling exists.
+const NONPUBLIC_QUALIFIED_ACCESSES = (
+    # ModelingToolkitBase: the FMI extension's variable metadata helpers.
+    :default_toterm,
+    :setinput,
+    :setoutput,
+    # ModelingToolkit's own stub that MTKFMIExt implements; it is documented API but has
+    # not been declared `public`, and an extension has no way to add a method unqualified.
+    :FMIComponent,
+    # Base: `Base.RefValue` has no public spelling.
+    :RefValue,
+)
+
 run_qa(
     ModelingToolkit;
     Aqua = Aqua,
     JET = JET,
     jet = true,
     jet_kwargs = (; target_defined_modules = true),
+    ei_kwargs = (;
+        all_qualified_accesses_are_public = (; ignore = NONPUBLIC_QUALIFIED_ACCESSES),
+    ),
     api_docs_kwargs = (; ignore = SYMBOLICS_OWNED_REEXPORTS),
 )