tests/comparators/test_ocaml.py

@@ -21,13 +21,32 @@ import pytest
 import subprocess
 
 from diffoscope.comparators.ocaml import OcamlInterfaceFile
+from diffoscope.comparators.binary import FilesystemFile
+from diffoscope.comparators.utils.specialize import specialize
 
 from ..utils.data import load_fixture, get_data
 from ..utils.tools import skip_unless_tool_is_at_least
 from ..utils.nonexisting import assert_non_existing
 
-cmi1 = load_fixture('test1.cmi')
-cmi2 = load_fixture('test2.cmi')
+
+def ocaml_fixture(prefix):
+    @pytest.fixture
+    def cmi(tmpdir):
+        input_ = str(tmpdir.join('{}.mli'.format(prefix)))
+        output = str(tmpdir.join('{}.cmi'.format(prefix)))
+
+        with open(input_, 'w') as f:
+            pass
+
+        subprocess.check_call(('ocamlc', '-c', input_))
+
+        return specialize(FilesystemFile(output))
+
+    return cmi
+
+
+cmi1 = ocaml_fixture('test1')
+cmi2 = ocaml_fixture('test2')
 
 
 def ocaml_version():

tests/data/ocaml_expected_diff

-@@ -1,5 +1,14 @@
- Unit name: Uchar
+@@ -1,5 +1,5 @@
+-Unit name: Test1
++Unit name: Test2
  Interfaces imported:
- 	84838649f9351de166bfa8b9f2c84db4	Uchar
+-	b5f47409a5d1c32a864ea3d2fbed44db	Test1
++	9ee19396ca59dbe57206a9a88d98a7d5	Test2
  	07ea9e20ae94d62c35cfecbe7d66d3ea	Pervasives
  	cbd5f2d6b649925222e1e9fb63b89db6	CamlinternalFormatBasics
-+Cmt unit name: Uchar
-+Cmt interfaces imported:
-+	cbd5f2d6b649925222e1e9fb63b89db6	CamlinternalFormatBasics
-+	07ea9e20ae94d62c35cfecbe7d66d3ea	Pervasives
-+	84838649f9351de166bfa8b9f2c84db4	Uchar
-+Source file: uchar.mli
-+Compilation flags: ../ocamlc -strict-sequence -absname -w +a-4-9-41-42-44-45-48 -g -warn-error A -bin-annot -nostdlib -safe-string -strict-formats -c uchar.mli
-+Load path: 
-+cmt interface digest: 84838649f9351de166bfa8b9f2c84db4

tests/utils/tools.py

@@ -27,6 +27,8 @@ import subprocess
 from distutils.spawn import find_executable
 from distutils.version import LooseVersion
 
+from diffoscope.tools import get_package_provider
+
 
 def file_version():
     return (
@@ -89,7 +91,7 @@ def skipif(*args, **kwargs):
 def skip_unless_tools_exist(*required):
     return skipif(
         tools_missing(*required),
-        reason="requires {}".format(" and ".join(required)),
+        reason=reason(*required),
         tools=required,
         check_env_for_missing_tools=True,
     )
@@ -97,7 +99,7 @@ def skip_unless_tools_exist(*required):
 
 def skip_if_tool_version_is(tool, actual_ver, target_ver, vcls=LooseVersion):
     if tools_missing(tool):
-        return skipif(True, reason="requires {}".format(tool), tools=(tool,))
+        return skipif(True, reason=reason(tool), tools=(tool,))
     if callable(actual_ver):
         actual_ver = actual_ver()
     return skipif(
@@ -111,13 +113,13 @@ def skip_if_tool_version_is(tool, actual_ver, target_ver, vcls=LooseVersion):
 
 def skip_unless_tool_is_at_least(tool, actual_ver, min_ver, vcls=LooseVersion):
     if tools_missing(tool) and module_is_not_importable(tool):
-        return skipif(True, reason="requires {}".format(tool), tools=(tool,))
+        return skipif(True, reason=reason(tool), tools=(tool,))
     if callable(actual_ver):
         actual_ver = actual_ver()
     return skipif(
         vcls(str(actual_ver)) < vcls(str(min_ver)),
-        reason="requires {} >= {} ({} detected)".format(
-            tool, min_ver, actual_ver
+        reason="{} >= {} ({} detected)".format(
+            reason(tool), min_ver, actual_ver
         ),
         tools=(tool,),
     )
@@ -125,13 +127,13 @@ def skip_unless_tool_is_at_least(tool, actual_ver, min_ver, vcls=LooseVersion):
 
 def skip_unless_tool_is_at_most(tool, actual_ver, max_ver, vcls=LooseVersion):
     if tools_missing(tool) and module_is_not_importable(tool):
-        return skipif(True, reason="requires {}".format(tool), tools=(tool,))
+        return skipif(True, reason=reason(tool), tools=(tool,))
     if callable(actual_ver):
         actual_ver = actual_ver()
     return skipif(
         vcls(str(actual_ver)) > vcls(str(max_ver)),
-        reason="requires {} <= {} ({} detected)".format(
-            tool, max_ver, actual_ver
+        reason="{} <= {} ({} detected)".format(
+            reason(tool), max_ver, actual_ver
         ),
         tools=(tool,),
     )
@@ -141,14 +143,14 @@ def skip_unless_tool_is_between(
     tool, actual_ver, min_ver, max_ver, vcls=LooseVersion
 ):
     if tools_missing(tool):
-        return skipif(True, reason="requires {}".format(tool), tools=(tool,))
+        return skipif(True, reason=reason(tool), tools=(tool,))
     if callable(actual_ver):
         actual_ver = actual_ver()
     return skipif(
         (vcls(str(actual_ver)) < vcls(str(min_ver)))
         or (vcls(str(actual_ver)) > vcls(str(max_ver))),
-        reason="requires {} >= {} >= {} ({} detected)".format(
-            min_ver, tool, max_ver, actual_ver
+        reason="{} min {} >= {} ({} detected)".format(
+            reason(tool), min_ver, max_ver, actual_ver
         ),
         tools=(tool,),
     )
@@ -194,10 +196,24 @@ def module_is_not_importable(x):
 def skip_unless_module_exists(name):
     return skipif(
         module_is_not_importable(name),
-        reason="requires {} module".format(name),
+        reason="requires {} Python module".format(name),
         tools=('{}_module'.format(name)),
     )
 
 
 def skip_unless_file_version_is_at_least(version):
     return skip_unless_tool_is_at_least('file', file_version, version)
+
+
+def reason(*tools):
+    xs = []
+
+    for x in tools:
+        provider = get_package_provider(x)
+        if provider is None:
+            xs.append(x)
+            continue
+
+        xs.append('{} (try installing {})'.format(x, provider))
+
+    return "requires {}".format(" and ".join(xs))