Do not require working fileno in tests

Pytest replaces stdin and stdout with fake class, ensuring stdin is not
used in tests. Tests work fine with file handle directly, fallback from
io.open to just pure class. It makes tests passing under pytest.

4 files changed, 19 insertions, 9 deletions

diff --git a/dnsviz/commands/graph.py b/dnsviz/commands/graph.py
index 2719b1d..7d3fe06 100644
--- a/dnsviz/commands/graph.py
+++ b/dnsviz/commands/graph.py
@@ -44,7 +44,7 @@ import dns.exception, dns.name
 from dnsviz.analysis import OfflineDomainNameAnalysis, DNS_RAW_VERSION
 from dnsviz.config import DNSVIZ_SHARE_PATH, JQUERY_PATH, JQUERY_UI_PATH, JQUERY_UI_CSS_PATH, RAPHAEL_PATH
 from dnsviz.format import latin1_binary_to_string as lb2s
-from dnsviz.util import get_trusted_keys, get_default_trusted_keys
+from dnsviz.util import get_trusted_keys, get_default_trusted_keys, io_try_buffered
 
 # If the import of DNSAuthGraph fails because of the lack of pygraphviz, it
 # will be reported later
@@ -154,8 +154,8 @@ class GraphArgHelper:
         self.parser = argparse.ArgumentParser(description='Graph the assessment of diagnostic DNS queries', prog=prog)
 
         # python3/python2 dual compatibility
-        stdin_buffer = io.open(sys.stdin.fileno(), 'rb', closefd=False)
-        stdout_buffer = io.open(sys.stdout.fileno(), 'wb', closefd=False)
+        stdin_buffer = io_try_buffered(sys.stdin, 'rb', closefd=False)
+        stdout_buffer = io_try_buffered(sys.stdout, 'wb', closefd=False)
 
         try:
             self.parser.add_argument('-f', '--names-file',
diff --git a/dnsviz/commands/grok.py b/dnsviz/commands/grok.py
index 6f2d8cd..8fc77c3 100644
--- a/dnsviz/commands/grok.py
+++ b/dnsviz/commands/grok.py
@@ -43,7 +43,7 @@ import dns.exception, dns.name
 
 from dnsviz.analysis import OfflineDomainNameAnalysis, DNS_RAW_VERSION
 from dnsviz.format import latin1_binary_to_string as lb2s
-from dnsviz.util import get_trusted_keys
+from dnsviz.util import get_trusted_keys, io_try_buffered
 
 # If the import of DNSAuthGraph fails because of the lack of pygraphviz, it
 # will be reported later
@@ -170,8 +170,8 @@ class GrokArgHelper:
         self.parser = argparse.ArgumentParser(description='Assess diagnostic DNS queries', prog=prog)
 
         # python3/python2 dual compatibility
-        stdin_buffer = io.open(sys.stdin.fileno(), 'rb', closefd=False)
-        stdout_buffer = io.open(sys.stdout.fileno(), 'wb', closefd=False)
+        stdin_buffer = io_try_buffered(sys.stdin, 'rb', closefd=False)
+        stdout_buffer = io_try_buffered(sys.stdout, 'wb', closefd=False)
 
         try:
             self.parser.add_argument('-f', '--names-file',
diff --git a/dnsviz/commands/print.py b/dnsviz/commands/print.py
index 3dcbb8d..80aa4a5 100644
--- a/dnsviz/commands/print.py
+++ b/dnsviz/commands/print.py
@@ -43,7 +43,7 @@ import dns.exception, dns.name
 
 from dnsviz.analysis import TTLAgnosticOfflineDomainNameAnalysis, DNS_RAW_VERSION
 from dnsviz.format import latin1_binary_to_string as lb2s
-from dnsviz.util import get_trusted_keys, get_default_trusted_keys
+from dnsviz.util import get_trusted_keys, get_default_trusted_keys, io_try_buffered
 
 # If the import of DNSAuthGraph fails because of the lack of pygraphviz, it
 # will be reported later
@@ -312,8 +312,8 @@ class PrintArgHelper:
         self.parser = argparse.ArgumentParser(description='Print the assessment of diagnostic DNS queries', prog=prog)
 
         # python3/python2 dual compatibility
-        stdin_buffer = io.open(sys.stdin.fileno(), 'rb', closefd=False)
-        stdout_buffer = io.open(sys.stdout.fileno(), 'wb', closefd=False)
+        stdin_buffer = io_try_buffered(sys.stdin, 'rb', closefd=False)
+        stdout_buffer = io_try_buffered(sys.stdout, 'wb', closefd=False)
 
         try:
             self.parser.add_argument('-f', '--names-file',
diff --git a/dnsviz/util.py b/dnsviz/util.py
index 8efed82..f4c6c71 100644
--- a/dnsviz/util.py
+++ b/dnsviz/util.py
@@ -184,3 +184,13 @@ def get_client_address(server):
         ip = IPAddr(s.getsockname()[0])
     s.close()
     return ip
+
+def io_try_buffered(f, mode, closefd=True):
+    """Try opening buffered reader, but allow unbuffered on failure.
+
+    Required to pass tests under pytest."""
+    try:
+        return io.open(f.fileno(), mode, closefd=closefd)
+    except io.UnsupportedOperation:
+        # raised by f.fileno()
+        return f