From 1ce3081e55970a10f8b081c3d6cf4af7d5bdae03 Mon Sep 17 00:00:00 2001
From: Eric Tune <etune@google.com>
Date: Mon, 4 Jan 2016 08:43:48 -0800
Subject: [PATCH] Do not delete text that fails preformat-balance

If preformat lines are unbalanced, do not delete all the lines from there to
end of file.  That might be the only copy of edits made by the user.

Do not print entire file contents for munge errors affecting entire file.
---
 cmd/mungedocs/mungedocs.go         |  8 ++++++--
 cmd/mungedocs/preformatted.go      |  2 +-
 cmd/mungedocs/preformatted_test.go | 19 ++++++++++++++++++-
 3 files changed, 25 insertions(+), 4 deletions(-)

diff --git a/cmd/mungedocs/mungedocs.go b/cmd/mungedocs/mungedocs.go
index 21e99d53388..92289fead66 100644
--- a/cmd/mungedocs/mungedocs.go
+++ b/cmd/mungedocs/mungedocs.go
@@ -119,8 +119,12 @@ func (f fileProcessor) visit(path string) error {
 			}
 			fmt.Printf("%s:\n", munge.name)
 			if *verbose {
-				fmt.Printf("INPUT: <<<%v>>>\n", mungeLines)
-				fmt.Printf("MUNGED: <<<%v>>>\n", after)
+				if len(mungeLines) <= 20 {
+					fmt.Printf("INPUT: <<<%v>>>\n", mungeLines)
+					fmt.Printf("MUNGED: <<<%v>>>\n", after)
+				} else {
+					fmt.Printf("not printing failed chunk: too many lines\n")
+				}
 			}
 			if err != nil {
 				fmt.Println(err)
diff --git a/cmd/mungedocs/preformatted.go b/cmd/mungedocs/preformatted.go
index 16955b70170..42dba178a6b 100644
--- a/cmd/mungedocs/preformatted.go
+++ b/cmd/mungedocs/preformatted.go
@@ -45,7 +45,7 @@ func updatePreformatted(filePath string, mlines mungeLines) (mungeLines, error)
 // If the file ends on a preformatted line, there must have been an imbalance.
 func checkPreformatBalance(filePath string, mlines mungeLines) (mungeLines, error) {
 	if len(mlines) > 0 && mlines[len(mlines)-1].preformatted {
-		return nil, fmt.Errorf("file ends in preformatted block")
+		return mlines, fmt.Errorf("unbalanced triple backtick delimiters")
 	}
 	return mlines, nil
 }
diff --git a/cmd/mungedocs/preformatted_test.go b/cmd/mungedocs/preformatted_test.go
index 9cedb9701b6..1df8f8059e2 100644
--- a/cmd/mungedocs/preformatted_test.go
+++ b/cmd/mungedocs/preformatted_test.go
@@ -69,12 +69,29 @@ func TestPreformattedImbalance(t *testing.T) {
 	}
 	for i, c := range cases {
 		in := getMungeLines(c.in)
-		_, err := checkPreformatBalance("filename.md", in)
+		out, err := checkPreformatBalance("filename.md", in)
 		if err != nil && c.ok {
 			t.Errorf("case[%d]: expected success", i)
 		}
 		if err == nil && !c.ok {
 			t.Errorf("case[%d]: expected failure", i)
 		}
+		// Even in case of misformat, return all the text,
+		// so that the user's work is not lost.
+		if !equalMungeLines(out, in) {
+			t.Errorf("case[%d]: expected munged text to be identical to input text", i)
+		}
 	}
 }
+
+func equalMungeLines(a, b mungeLines) bool {
+	if len(a) != len(b) {
+		return false
+	}
+	for i := range a {
+		if a[i] != b[i] {
+			return false
+		}
+	}
+	return true
+}