[lit] Extend internal diff to support -U

When using lit's internal shell, RUN lines like the following
accidentally execute an external `diff` instead of lit's internal
`diff`:

```
 # RUN: program | diff -U1 file -
```

Such cases exist now, in `clang/test/Analysis` for example.  We are
preparing patches to ensure lit's internal `diff` is called in such
cases, which will then fail because lit's internal `diff` doesn't
recognize `-U` as a command-line option.  This patch adds `-U`
support.

Reviewed By: rnk

Differential Revision: https://reviews.llvm.org/D68668

llvm-svn: 374392

utils/lit/lit/builtin_commands/diff.py

@@ -10,6 +10,7 @@ class DiffFlags():
         self.ignore_all_space = False
         self.ignore_space_change = False
         self.unified_diff = False
+        self.num_context_lines = 3
         self.recursive_diff = False
         self.strip_trailing_cr = False
 
@@ -48,7 +49,10 @@ def compareTwoBinaryFiles(flags, filepaths, filelines):
     exitCode = 0
     if hasattr(difflib, 'diff_bytes'):
         # python 3.5 or newer
-        diffs = difflib.diff_bytes(difflib.unified_diff, filelines[0], filelines[1], filepaths[0].encode(), filepaths[1].encode())
+        diffs = difflib.diff_bytes(difflib.unified_diff, filelines[0],
+                                   filelines[1], filepaths[0].encode(),
+                                   filepaths[1].encode(),
+                                   n = flags.num_context_lines)
         diffs = [diff.decode(errors="backslashreplace") for diff in diffs]
     else:
         # python 2.7
@@ -56,7 +60,8 @@ def compareTwoBinaryFiles(flags, filepaths, filelines):
             func = difflib.unified_diff
         else:
             func = difflib.context_diff
-        diffs = func(filelines[0], filelines[1], filepaths[0], filepaths[1])
+        diffs = func(filelines[0], filelines[1], filepaths[0], filepaths[1],
+                     n = flags.num_context_lines)
 
     for diff in diffs:
         sys.stdout.write(diff)
@@ -88,7 +93,8 @@ def compareTwoTextFiles(flags, filepaths, filelines_bin, encoding):
         filelines[idx]= [f(line) for line in lines]
 
     func = difflib.unified_diff if flags.unified_diff else difflib.context_diff
-    for diff in func(filelines[0], filelines[1], filepaths[0], filepaths[1]):
+    for diff in func(filelines[0], filelines[1], filepaths[0], filepaths[1],
+                     n = flags.num_context_lines):
         sys.stdout.write(diff)
         exitCode = 1
     return exitCode
@@ -171,7 +177,7 @@ def compareDirTrees(flags, dir_trees, base_paths=["", ""]):
 def main(argv):
     args = argv[1:]
     try:
-        opts, args = getopt.gnu_getopt(args, "wbur", ["strip-trailing-cr"])
+        opts, args = getopt.gnu_getopt(args, "wbuU:r", ["strip-trailing-cr"])
     except getopt.GetoptError as err:
         sys.stderr.write("Unsupported: 'diff': %s\n" % str(err))
         sys.exit(1)
@@ -185,6 +191,16 @@ def main(argv):
             flags.ignore_space_change = True
         elif o == "-u":
             flags.unified_diff = True
+        elif o.startswith("-U"):
+            flags.unified_diff = True
+            try:
+                flags.num_context_lines = int(a)
+                if flags.num_context_lines < 0:
+                    raise ValueException
+            except:
+                sys.stderr.write("Error: invalid '-U' argument: {}\n"
+                                 .format(a))
+                sys.exit(1)
         elif o == "-r":
             flags.recursive_diff = True
         elif o == "--strip-trailing-cr":

utils/lit/tests/Inputs/shtest-shell/diff-unified.txt

@@ -0,0 +1,38 @@
+# RUN: echo 1 > %t.foo
+# RUN: echo 2 >> %t.foo
+# RUN: echo 3 >> %t.foo
+# RUN: echo 4 >> %t.foo
+# RUN: echo 5 >> %t.foo
+# RUN: echo 6 foo >> %t.foo
+# RUN: echo 7 >> %t.foo
+# RUN: echo 8 >> %t.foo
+# RUN: echo 9 >> %t.foo
+# RUN: echo 10 >> %t.foo
+# RUN: echo 11 >> %t.foo
+
+# RUN: echo 1 > %t.bar
+# RUN: echo 2 >> %t.bar
+# RUN: echo 3 >> %t.bar
+# RUN: echo 4 >> %t.bar
+# RUN: echo 5 >> %t.bar
+# RUN: echo 6 bar >> %t.bar
+# RUN: echo 7 >> %t.bar
+# RUN: echo 8 >> %t.bar
+# RUN: echo 9 >> %t.bar
+# RUN: echo 10 >> %t.bar
+# RUN: echo 11 >> %t.bar
+
+# Default is 3 lines of context.
+# RUN: diff -u %t.foo %t.bar && false || true
+
+# Override default of 3 lines of context.
+# RUN: diff -U 2 %t.foo %t.bar && false || true
+# RUN: diff -U4 %t.foo %t.bar && false || true
+# RUN: diff -U0 %t.foo %t.bar && false || true
+
+# Check bad -U argument.
+# RUN: diff -U 30.1 %t.foo %t.foo && false || true
+# RUN: diff -U-1 %t.foo %t.foo && false || true
+
+# Fail so lit will print output.
+# RUN: false

utils/lit/tests/max-failures.py

@@ -8,7 +8,7 @@
 #
 # END.
 
-# CHECK: Failing Tests (30)
+# CHECK: Failing Tests (31)
 # CHECK: Failing Tests (1)
 # CHECK: Failing Tests (2)
 # CHECK: error: Option '--max-failures' requires positive integer

utils/lit/tests/shtest-shell.py

@@ -331,6 +331,82 @@
 
 # CHECK: PASS: shtest-shell :: diff-r.txt
 
+
+# CHECK: FAIL: shtest-shell :: diff-unified.txt
+
+# CHECK: *** TEST 'shtest-shell :: diff-unified.txt' FAILED ***
+
+# CHECK: $ "diff" "-u" "{{[^"]*}}.foo" "{{[^"]*}}.bar"
+# CHECK: # command output:
+# CHECK: @@ {{.*}} @@
+# CHECK-NEXT: 3
+# CHECK-NEXT: 4
+# CHECK-NEXT: 5
+# CHECK-NEXT: -6 foo
+# CHECK-NEXT: +6 bar
+# CHECK-NEXT: 7
+# CHECK-NEXT: 8
+# CHECK-NEXT: 9
+# CHECK-EMPTY:
+# CHECK-NEXT: error: command failed with exit status: 1
+# CHECK-NEXT: $ "true"
+
+# CHECK: $ "diff" "-U" "2" "{{[^"]*}}.foo" "{{[^"]*}}.bar"
+# CHECK: # command output:
+# CHECK: @@ {{.*}} @@
+# CHECK-NEXT: 4
+# CHECK-NEXT: 5
+# CHECK-NEXT: -6 foo
+# CHECK-NEXT: +6 bar
+# CHECK-NEXT: 7
+# CHECK-NEXT: 8
+# CHECK-EMPTY:
+# CHECK-NEXT: error: command failed with exit status: 1
+# CHECK-NEXT: $ "true"
+
+# CHECK: $ "diff" "-U4" "{{[^"]*}}.foo" "{{[^"]*}}.bar"
+# CHECK: # command output:
+# CHECK: @@ {{.*}} @@
+# CHECK-NEXT: 2
+# CHECK-NEXT: 3
+# CHECK-NEXT: 4
+# CHECK-NEXT: 5
+# CHECK-NEXT: -6 foo
+# CHECK-NEXT: +6 bar
+# CHECK-NEXT: 7
+# CHECK-NEXT: 8
+# CHECK-NEXT: 9
+# CHECK-NEXT: 10
+# CHECK-EMPTY:
+# CHECK-NEXT: error: command failed with exit status: 1
+# CHECK-NEXT: $ "true"
+
+# CHECK: $ "diff" "-U0" "{{[^"]*}}.foo" "{{[^"]*}}.bar"
+# CHECK: # command output:
+# CHECK: @@ {{.*}} @@
+# CHECK-NEXT: -6 foo
+# CHECK-NEXT: +6 bar
+# CHECK-EMPTY:
+# CHECK-NEXT: error: command failed with exit status: 1
+# CHECK-NEXT: $ "true"
+
+# CHECK: $ "diff" "-U" "30.1" "{{[^"]*}}" "{{[^"]*}}"
+# CHECK: # command stderr:
+# CHECK: Error: invalid '-U' argument: 30.1
+# CHECK: error: command failed with exit status: 1
+# CHECK: $ "true"
+
+# CHECK: $ "diff" "-U-1" "{{[^"]*}}" "{{[^"]*}}"
+# CHECK: # command stderr:
+# CHECK: Error: invalid '-U' argument: -1
+# CHECK: error: command failed with exit status: 1
+# CHECK: $ "true"
+
+# CHECK: $ "false"
+
+# CHECK: ***
+
+
 # CHECK: FAIL: shtest-shell :: error-0.txt
 # CHECK: *** TEST 'shtest-shell :: error-0.txt' FAILED ***
 # CHECK: $ "not-a-real-command"
@@ -410,4 +486,4 @@
 # CHECK: PASS: shtest-shell :: sequencing-0.txt
 # CHECK: XFAIL: shtest-shell :: sequencing-1.txt
 # CHECK: PASS: shtest-shell :: valid-shell.txt
-# CHECK: Failing Tests (30)
+# CHECK: Failing Tests (31)