[llvm-cov] format cells in report with 0/0 branches/functions/lines d…

…ifferenly (gray instead red) and make the table a bit nicer (#75780)

llvm/test/tools/llvm-cov/coverage_watermark.test

@@ -13,29 +13,47 @@ INVALID-ARRANGE: error: -coverage-watermark: invalid number range '10,20', must
 RUN: llvm-cov show %S/Inputs/templateInstantiations.covmapping -instr-profile %S/Inputs/templateInstantiations.profdata -format html -show-region-summary -show-instantiation-summary -o %t.html.dir -path-equivalence=/tmp,%S %S/showTemplateInstantiations.cpp
 RUN: FileCheck -check-prefix=ORIGIN %s -input-file %t.html.dir/index.html
 
+ORIGIN: Totals
+ORIGIN: <td class='column-entry-green'>
+ORIGIN: 100.00% (2/2)
 ORIGIN: <td class='column-entry-green'>
 ORIGIN: 100.00% (3/3)
 ORIGIN: <td class='column-entry-red'>
 ORIGIN: 75.00% (9/12)
 ORIGIN: <td class='column-entry-red'>
 ORIGIN: 66.67% (4/6)
+ORIGIN: <td class='column-entry-gray'>
+ORIGIN: - (0/0)
+ORIGIN: </tr>
 
-RUN: llvm-cov show %S/Inputs/templateInstantiations.covmapping -instr-profile %S/Inputs/templateInstantiations.profdata -format html -show-region-summary -show-instantiation-summary -o %t.html.dir -path-equivalence=/tmp,%S -coverage-watermark 80,60 %S/showTemplateInstantiations.cpp
+RUN: llvm-cov show %S/Inputs/templateInstantiations.covmapping -instr-profile %S/Inputs/templateInstantiations.profdata -format html -show-region-summary -show-instantiation-summary -o %t.html.dir -path-equivalence=/tmp,%S -coverage-watermark 80,70 %S/showTemplateInstantiations.cpp
 RUN: FileCheck -check-prefix=DOWNGRADE1 %s -input-file %t.html.dir/index.html
 
+DOWNGRADE:1 Totals
+DOWNGRADE1: <td class='column-entry-green'>
+DOWNGRADE1: 100.00% (2/2)
 DOWNGRADE1: <td class='column-entry-green'>
 DOWNGRADE1: 100.00% (3/3)
 DOWNGRADE1: <td class='column-entry-yellow'>
 DOWNGRADE1: 75.00% (9/12)
 DOWNGRADE1: <td class='column-entry-red'>
 DOWNGRADE1: 66.67% (4/6)
+DOWNGRADE1: <td class='column-entry-gray'>
+DOWNGRADE1: - (0/0)
+DOWNGRADE1: </tr>
 
 RUN: llvm-cov show %S/Inputs/templateInstantiations.covmapping -instr-profile %S/Inputs/templateInstantiations.profdata -format html -show-region-summary -show-instantiation-summary -o %t.html.dir -path-equivalence=/tmp,%S -coverage-watermark 70,50 %S/showTemplateInstantiations.cpp
 RUN: FileCheck -check-prefix=DOWNGRADE2 %s -input-file %t.html.dir/index.html
 
+DOWNGRADE:1 Totals
+DOWNGRADE2: <td class='column-entry-green'>
+DOWNGRADE2: 100.00% (2/2)
 DOWNGRADE2: <td class='column-entry-green'>
 DOWNGRADE2: 100.00% (3/3)
 DOWNGRADE2: <td class='column-entry-green'>
 DOWNGRADE2: 75.00% (9/12)
 DOWNGRADE2: <td class='column-entry-yellow'>
 DOWNGRADE2: 66.67% (4/6)
+DOWNGRADE1: <td class='column-entry-gray'>
+DOWNGRADE1: - (0/0)
+DOWNGRADE1: </tr>

llvm/tools/llvm-cov/SourceCoverageViewHTML.cpp

@@ -130,10 +130,14 @@ table {
 .light-row {
   background: #ffffff;
   border: 1px solid #dbdbdb;
+  border-left: none;
+  border-right: none;
 }
 .light-row-bold {
   background: #ffffff;
   border: 1px solid #dbdbdb;
+  border-left: none;
+  border-right: none;
   font-weight: bold;
 }
 .column-entry {
@@ -147,21 +151,28 @@ table {
   text-align: left;
   background-color: #ffffd0;
 }
-.column-entry-yellow:hover {
+.column-entry-yellow:hover, tr:hover .column-entry-yellow {
   background-color: #fffff0;
 }
 .column-entry-red {
   text-align: left;
   background-color: #ffd0d0;
 }
-.column-entry-red:hover {
+.column-entry-red:hover, tr:hover .column-entry-red {
   background-color: #fff0f0;
 }
+.column-entry-gray {
+  text-align: left;
+  background-color: #fbfbfb;
+}
+.column-entry-gray:hover, tr:hover .column-entry-gray {
+  background-color: #f0f0f0;
+}
 .column-entry-green {
   text-align: left;
   background-color: #d0ffd0;
 }
-.column-entry-green:hover {
+.column-entry-green:hover, tr:hover .column-entry-green {
   background-color: #f0fff0;
 }
 .line-number {
@@ -232,6 +243,9 @@ td:last-child {
 tr:hover {
   background-color: #f0f0f0;
 }
+tr:last-child {
+  border-bottom: none;
+}
 )";
 
 const char *EndHeader = "</head>";
@@ -309,7 +323,9 @@ void emitTableRow(raw_ostream &OS, const CoverageViewOptions &Opts,
           RSO << '(' << Hit << '/' << Total << ')';
         }
         const char *CellClass = "column-entry-yellow";
-        if (Pctg >= Opts.HighCovWatermark)
+        if (!Total)
+          CellClass = "column-entry-gray";
+        else if (Pctg >= Opts.HighCovWatermark)
           CellClass = "column-entry-green";
         else if (Pctg < Opts.LowCovWatermark)
           CellClass = "column-entry-red";