Add colourful formatter "screen"

Prints vulnerabilities with ANSI colour codes for the terminal.

Not crazily colourful: just tries to highlight the important stuff.

Repeated filenames aren't printed.
Colour scheme might not be to everyone's taste.

Author: bcaller

.coveragerc

@@ -15,4 +15,5 @@ source =
     ./tests
 omit =
     pyt/formatters/json.py
+    pyt/formatters/screen.py
     pyt/formatters/text.py

pyt/formatters/screen.py

@@ -0,0 +1,104 @@
+"""This formatter outputs the issues as color-coded text."""
+from ..vulnerabilities.vulnerability_helper import SanitisedVulnerability, UnknownVulnerability
+
+RESET = '\033[0m'
+BOLD = '\033[1m'
+UNDERLINE = '\033[4m'
+DANGER = '\033[31m'
+GOOD = '\033[32m'
+HIGHLIGHT = '\033[45;1m'
+RED_ON_WHITE = '\033[31m\033[107m'
+
+
+def color(string, color_string):
+    return color_string + str(string) + RESET
+
+
+def report(
+    vulnerabilities,
+    fileobj,
+    print_sanitised,
+):
+    """
+    Prints issues in color-coded text format.
+
+    Args:
+        vulnerabilities: list of vulnerabilities to report
+        fileobj: The output file object, which may be sys.stdout
+    """
+    n_vulnerabilities = len(vulnerabilities)
+    unsanitised_vulnerabilities = [v for v in vulnerabilities if not isinstance(v, SanitisedVulnerability)]
+    n_unsanitised = len(unsanitised_vulnerabilities)
+    n_sanitised = n_vulnerabilities - n_unsanitised
+    heading = "{} vulnerabilit{} found{}.\n".format(
+        'No' if n_unsanitised == 0 else n_unsanitised,
+        'y' if n_unsanitised == 1 else 'ies',
+        " (plus {} sanitised)".format(n_sanitised) if n_sanitised else "",
+    )
+    vulnerabilities_to_print = vulnerabilities if print_sanitised else unsanitised_vulnerabilities
+    with fileobj:
+        for i, vulnerability in enumerate(vulnerabilities_to_print, start=1):
+            fileobj.write(vulnerability_to_str(i, vulnerability))
+
+        if n_unsanitised == 0:
+            fileobj.write(color(heading, GOOD))
+        else:
+            fileobj.write(color(heading, DANGER))
+
+
+def vulnerability_to_str(i, vulnerability):
+    lines = []
+    lines.append(color('Vulnerability {}'.format(i), UNDERLINE))
+    lines.append('File: {}'.format(color(vulnerability.source.path, BOLD)))
+    lines.append(
+        'User input at line {}, source "{}":'.format(
+            vulnerability.source.line_number,
+            color(vulnerability.source_trigger_word, HIGHLIGHT),
+        )
+    )
+    lines.append('\t{}'.format(color(vulnerability.source.label, RED_ON_WHITE)))
+    if vulnerability.reassignment_nodes:
+        previous_path = None
+        lines.append('Reassigned in:')
+        for node in vulnerability.reassignment_nodes:
+            if node.path != previous_path:
+                lines.append('\tFile: {}'.format(node.path))
+                previous_path = node.path
+            label = node.label
+            if (
+                isinstance(vulnerability, SanitisedVulnerability) and
+                node.label == vulnerability.sanitiser.label
+            ):
+                label = color(label, GOOD)
+            lines.append(
+                '\t  Line {}:\t{}'.format(
+                    node.line_number,
+                    label,
+                )
+            )
+    if vulnerability.source.path != vulnerability.sink.path:
+        lines.append('File: {}'.format(color(vulnerability.sink.path, BOLD)))
+    lines.append(
+        'Reaches line {}, sink "{}"'.format(
+            vulnerability.sink.line_number,
+            color(vulnerability.sink_trigger_word, HIGHLIGHT),
+        )
+    )
+    lines.append('\t{}'.format(
+        color(vulnerability.sink.label, RED_ON_WHITE)
+    ))
+    if isinstance(vulnerability, SanitisedVulnerability):
+        lines.append(
+            'This vulnerability is {}{} by {}'.format(
+                color('potentially ', BOLD) if not vulnerability.confident else '',
+                color('sanitised', GOOD),
+                color(vulnerability.sanitiser.label, BOLD),
+            )
+        )
+    elif isinstance(vulnerability, UnknownVulnerability):
+        lines.append(
+            'This vulnerability is unknown due to "{}"'.format(
+                color(vulnerability.unknown_assignment.label, BOLD),
+            )
+        )
+    return '\n'.join(lines) + '\n\n'