[lmi-commits] [lmi] master 0fcb08d 1/2: Require any report table to contain at least one column

[Greg Chicares]

branch: master
commit 0fcb08d5b5d215e5a482602fb41c778a682c64e0
Author: Gregory W. Chicares <address@hidden>
Commit: Gregory W. Chicares <address@hidden>

    Require any report table to contain at least one column
    
    Asserted a precondition; unit-tested the assertion. The reproducible
    test case here:
      https://lists.nongnu.org/archive/html/lmi/2019-05/msg00010.html
    now results in this improved diagnostic:
      Report table would contain no columns.
---
 report_table.cpp      | 7 +++++++
 report_table_test.cpp | 8 ++++++++
 2 files changed, 15 insertions(+)

diff --git a/report_table.cpp b/report_table.cpp
index 29e30ef..06c681f 100644
--- a/report_table.cpp
+++ b/report_table.cpp
@@ -95,6 +95,8 @@ std::vector<int> apportion(std::vector<int> const& votes, int 
total_seats)
 /// First, allocate adequate width to each inelastic column; then
 /// distribute any excess width left over among elastic columns.
 ///
+/// Asserted precondition: the number of columns passed is not zero.
+///
 /// Notes on arguments:
 ///   all_columns: the width of each inelastic column reflects:
 ///    - the header width, and
@@ -114,6 +116,11 @@ std::vector<int> set_column_widths
 {
     LMI_ASSERT(minimum_margin <= desired_margin);
     int const cardinality = lmi::ssize(all_columns);
+    if(0 == cardinality)
+        {
+        alarum() << "Report table would contain no columns." << LMI_FLUSH;
+        }
+
     int data_width = 0;
     int n_columns_to_show = 0;
     for(int j = 0, cum_min_width = 0; j < cardinality; ++j)
diff --git a/report_table_test.cpp b/report_table_test.cpp
index a33d4c6..ba94798 100644
--- a/report_table_test.cpp
+++ b/report_table_test.cpp
@@ -230,6 +230,14 @@ void report_table_test::test_column_widths_generally()
         ,"Not enough room for even the first column."
         );
 
+    // Report with zero columns.
+    v = bloat({}, {});
+    BOOST_TEST_THROW
+        (set_column_widths(v, 1, 2, 1)
+        ,std::runtime_error
+        ,"Report table would contain no columns."
+        );
+
     // Minimum margin greater than one.
     v = bloat({1, 2, 3}, {0, 0, 0});
     observed = set_column_widths(v, 16, 5, 3);