add get VariablePrimalStart

Author: andrewrosemberg

src/MOI_wrapper.jl

@@ -323,6 +323,22 @@ function MOI.supports(
     return MOI.supports(model.optimizer, attr, tp)
 end
 
+function MOI.get(
+    model::Optimizer,
+    attr::MOI.VariablePrimalStart,
+    v::MOI.VariableIndex,
+)
+    if _variable_in_model(model, v)
+        return MOI.get(model.optimizer, attr, v)
+    elseif _parameter_in_model(model, v)
+        # this is effectivelly a no-op, but we do validation
+        _val = model.parameters[p_idx(v)]
+        return _val
+    else
+        error("Variable not in the model")
+    end
+end
+
 function MOI.set(
     model::Optimizer,
     attr::MOI.VariablePrimalStart,

test/jump_tests.jl

@@ -430,8 +430,7 @@ function test_jump_set_variable_start_value()
     @test_throws ErrorException(
         "The parameter $(index(p)) value is 0.0, but trying to set VariablePrimalStart 1.0",
     ) set_start_value(p, 1.0)
-    err = ErrorException("MathOptInterface.VariablePrimalStart() is not supported for parameters")
-    @test_throws err start_value(p)
+    @test start_value(p) == 0.0
     return
 end