fix: improve error message when dis package missing (MODFLOW-ORG#2813)

Stop with an informative error if grid discretization is missing after loading the model input file's packages block.

Author: wpbonelli

doc/ReleaseNotes/develop.toml

@@ -63,3 +63,8 @@ description = "Avoids an unhandled and unnecessary exception in cases where a GW
 section = "fixes"
 subsection = "netcdf"
 description = "Fix an indexing issue in structured NetCDF export where READASARRAYS packages (RCHA, EVTA) with time-varying per-period arrays would crash with a NetCDF edge-exceeds-bound error when writing any stress period after the first."
+
+[[items]]
+section = "fixes"
+subsection = "basic"
+description = "Stop with an informative error if a discretization package is missing after loading the model input file's PACKAGES block."

src/Utilities/Idm/ModelPackageInputs.f90

@@ -277,17 +277,21 @@ subroutine modelpkgs_create(this, ftypes)
     integer(I4B), dimension(:), allocatable :: cunit_idxs, indx
     character(len=LENPACKAGETYPE) :: ftype
     integer(I4B) :: n, m
-    logical(LGP) :: found
+    logical(LGP) :: found, has_dis
 
     ! allocate
     allocate (cunit_idxs(0))
+    has_dis = .false.
 
     ! identify input packages and check that each is supported
     do n = 1, size(ftypes)
       ! type from model nam file packages block
       ftype = ftypes(n)
       found = .false.
 
+      ! check for discretization package (any type starting with 'DIS')
+      if (ftype(1:3) == 'DIS') has_dis = .true.
+
       ! search supported types for this filetype
       do m = 1, this%niunit
         if (this%cunit(m) == ftype) then
@@ -317,6 +321,15 @@ subroutine modelpkgs_create(this, ftypes)
       end if
     end do
 
+    ! check that a discretization package is specified
+    if (.not. has_dis) then
+      write (errmsg, '(3a)') &
+        'Discretization package not specified for model "', &
+        trim(this%modelname), '".'
+      call store_error(errmsg)
+      call store_error_filename(this%modelfname)
+    end if
+
     ! allocate the pkglist
     allocate (this%pkglist(size(cunit_idxs)))