Add support for JSON reporter

This exposes an additional reporter that's provided by coverage.py. THe
implementation is basically a carbon copy of the code that powers the
XML implementation.

docs/config.rst

@@ -56,9 +56,9 @@ The complete list of command line options is:
 
   --cov=PATH            Measure coverage for filesystem path. (multi-allowed)
   --cov-report=type     Type of report to generate: term, term-missing,
-                        annotate, html, xml, lcov (multi-allowed). term, term-
+                        annotate, html, xml, json, lcov (multi-allowed). term, term-
                         missing may be followed by ":skip-covered". annotate,
-                        html, xml and lcov may be followed by ":DEST" where DEST
+                        html, xml, json and lcov may be followed by ":DEST" where DEST
                         specifies the output location. Use --cov-report= to
                         not generate any output.
   --cov-config=path     Config file for coverage. Default: .coveragerc

docs/reporting.rst

@@ -3,7 +3,7 @@ Reporting
 
 It is possible to generate any combination of the reports for a single test run.
 
-The available reports are terminal (with or without missing line numbers shown), HTML, XML, LCOV and
+The available reports are terminal (with or without missing line numbers shown), HTML, XML, JSON, LCOV and
 annotated source code.
 
 The terminal report without line numbers (default)::
@@ -53,16 +53,18 @@ These four report options output to files without showing anything on the termin
 
     pytest --cov-report html
             --cov-report xml
+            --cov-report json
             --cov-report lcov
             --cov-report annotate
             --cov=myproj tests/
 
-The output location for each of these reports can be specified. The output location for the XML and LCOV
+The output location for each of these reports can be specified. The output location for the XML, JSON and LCOV
 report is a file. Where as the output location for the HTML and annotated source code reports are
 directories::
 
     pytest --cov-report html:cov_html
             --cov-report xml:cov.xml
+            --cov-report json:cov.json
             --cov-report lcov:cov.info
             --cov-report annotate:cov_annotate
             --cov=myproj tests/

src/pytest_cov/engine.py

@@ -196,6 +196,13 @@ def summary(self, stream):
                 total = self.cov.xml_report(ignore_errors=True, outfile=output)
             stream.write('Coverage XML written to file %s\n' % (self.cov.config.xml_output if output is None else output))
 
+        # Produce json report if wanted
+        if 'json' in self.cov_report:
+            output = self.cov_report['json']
+            with _backup(self.cov, "config"):
+                total = self.cov.json_report(ignore_errors=True, outfile=output)
+            stream.write('Coverage JSON written to file %s\n' % (self.cov.config.json_output if output is None else output))
+
         # Produce lcov report if wanted.
         if 'lcov' in self.cov_report:
             output = self.cov_report['lcov']

src/pytest_cov/plugin.py

@@ -29,7 +29,7 @@ class CovReportWarning(PytestCovWarning):
 
 
 def validate_report(arg):
-    file_choices = ['annotate', 'html', 'xml', 'lcov']
+    file_choices = ['annotate', 'html', 'xml', 'json', 'lcov']
     term_choices = ['term', 'term-missing']
     term_modifier_choices = ['skip-covered']
     all_choices = term_choices + file_choices
@@ -99,9 +99,9 @@ def pytest_addoption(parser):
     group.addoption('--cov-report', action=StoreReport, default={},
                     metavar='TYPE', type=validate_report,
                     help='Type of report to generate: term, term-missing, '
-                         'annotate, html, xml, lcov (multi-allowed). '
+                         'annotate, html, xml, json, lcov (multi-allowed). '
                          'term, term-missing may be followed by ":skip-covered". '
-                         'annotate, html, xml and lcov may be followed by ":DEST" '
+                         'annotate, html, xml, json and lcov may be followed by ":DEST" '
                          'where DEST specifies the output location. '
                          'Use --cov-report= to not generate any output.')
     group.addoption('--cov-config', action='store', default='.coveragerc',

tests/test_pytest_cov.py

@@ -151,6 +151,7 @@ def test_foo(cov):
 PARENT_SCRIPT_RESULT = '9 * 100%'
 DEST_DIR = 'cov_dest'
 XML_REPORT_NAME = 'cov.xml'
+JSON_REPORT_NAME = 'cov.json'
 LCOV_REPORT_NAME = 'cov.info'
 
 xdist_params = pytest.mark.parametrize('opts', [
@@ -346,6 +347,23 @@ def test_xml_output_dir(testdir):
     assert result.ret == 0
 
 
+def test_json_output_dir(testdir):
+    script = testdir.makepyfile(SCRIPT)
+
+    result = testdir.runpytest('-v',
+                               '--cov=%s' % script.dirpath(),
+                               '--cov-report=json:' + JSON_REPORT_NAME,
+                               script)
+
+    result.stdout.fnmatch_lines([
+        '*- coverage: platform *, python * -*',
+        'Coverage JSON written to file ' + JSON_REPORT_NAME,
+        '*10 passed*',
+    ])
+    assert testdir.tmpdir.join(JSON_REPORT_NAME).check()
+    assert result.ret == 0
+
+
 @pytest.mark.skipif("coverage.version_info < (6, 3)")
 def test_lcov_output_dir(testdir):
     script = testdir.makepyfile(SCRIPT)