[WIP RFC PATCH 1/7] dir-iterator: add pedantic option to dir_iterator_begin

["Ævar Arnfjörð Bjarmason" <avarab@gmail.com>]

From: Matheus Tavares <matheus.bernardino@usp.br>

Add the pedantic option to dir-iterator's initialization function,
dir_iterator_begin. When this option is set to true,
dir_iterator_advance will immediately return ITER_ERROR when failing to
fetch the next entry. When set to false, dir_iterator_advance will emit
a warning and keep looking for the next entry.

Also adjust refs/files-backend.c to the new dir_iterator_begin
signature.

Signed-off-by: Matheus Tavares <matheus.bernardino@usp.br>
---
 dir-iterator.c       | 23 +++++++++++++++++++++--
 dir-iterator.h       | 16 +++++++++++++---
 refs/files-backend.c |  2 +-
 3 files changed, 35 insertions(+), 6 deletions(-)

diff --git a/dir-iterator.c b/dir-iterator.c
index f2dcd82fde..070a656555 100644
--- a/dir-iterator.c
+++ b/dir-iterator.c
@@ -48,6 +48,13 @@ struct dir_iterator_int {
 	 * that will be included in this iteration.
 	 */
 	struct dir_iterator_level *levels;
+
+	/*
+	 * Boolean value to define dir-iterator's behaviour when failing to
+	 * fetch next entry. See comments on dir_iterator_begin at
+	 * dir-iterator.h
+	 */
+	int pedantic;
 };
 
 int dir_iterator_advance(struct dir_iterator *dir_iterator)
@@ -71,6 +78,8 @@ int dir_iterator_advance(struct dir_iterator *dir_iterator)
 
 			level->dir = opendir(iter->base.path.buf);
 			if (!level->dir && errno != ENOENT) {
+				if (iter->pedantic)
+					goto error_out;
 				warning("error opening directory %s: %s",
 					iter->base.path.buf, strerror(errno));
 				/* Popping the level is handled below */
@@ -122,6 +131,8 @@ int dir_iterator_advance(struct dir_iterator *dir_iterator)
 			if (!de) {
 				/* This level is exhausted; pop up a level. */
 				if (errno) {
+					if (iter->pedantic)
+						goto error_out;
 					warning("error reading directory %s: %s",
 						iter->base.path.buf, strerror(errno));
 				} else if (closedir(level->dir))
@@ -139,10 +150,13 @@ int dir_iterator_advance(struct dir_iterator *dir_iterator)
 
 			strbuf_addstr(&iter->base.path, de->d_name);
 			if (lstat(iter->base.path.buf, &iter->base.st) < 0) {
-				if (errno != ENOENT)
+				if (errno != ENOENT) {
+					if (iter->pedantic)
+						goto error_out;
 					warning("error reading path '%s': %s",
 						iter->base.path.buf,
 						strerror(errno));
+				}
 				continue;
 			}
 
@@ -159,6 +173,10 @@ int dir_iterator_advance(struct dir_iterator *dir_iterator)
 			return ITER_OK;
 		}
 	}
+
+error_out:
+	dir_iterator_abort(dir_iterator);
+	return ITER_ERROR;
 }
 
 int dir_iterator_abort(struct dir_iterator *dir_iterator)
@@ -182,7 +200,7 @@ int dir_iterator_abort(struct dir_iterator *dir_iterator)
 	return ITER_DONE;
 }
 
-struct dir_iterator *dir_iterator_begin(const char *path)
+struct dir_iterator *dir_iterator_begin(const char *path, int pedantic)
 {
 	struct dir_iterator_int *iter = xcalloc(1, sizeof(*iter));
 	struct dir_iterator *dir_iterator = &iter->base;
@@ -195,6 +213,7 @@ struct dir_iterator *dir_iterator_begin(const char *path)
 
 	ALLOC_GROW(iter->levels, 10, iter->levels_alloc);
 
+	iter->pedantic = pedantic;
 	iter->levels_nr = 1;
 	iter->levels[0].initialized = 0;
 
diff --git a/dir-iterator.h b/dir-iterator.h
index 970793d07a..50ca8e1a27 100644
--- a/dir-iterator.h
+++ b/dir-iterator.h
@@ -19,7 +19,7 @@
  * A typical iteration looks like this:
  *
  *     int ok;
- *     struct iterator *iter = dir_iterator_begin(path);
+ *     struct iterator *iter = dir_iterator_begin(path, 0);
  *
  *     while ((ok = dir_iterator_advance(iter)) == ITER_OK) {
  *             if (want_to_stop_iteration()) {
@@ -65,9 +65,15 @@ struct dir_iterator {
  * The iteration includes all paths under path, not including path
  * itself and not including "." or ".." entries.
  *
- * path is the starting directory. An internal copy will be made.
+ * Parameters are:
+ * - path is the starting directory. An internal copy will be made.
+ * - pedantic is a boolean value. If true, dir-iterator will free
+ *   resources and return ITER_ERROR immediately, in case of an error
+ *   while trying to fetch the next entry in dir_iterator_advance. If
+ *   false, it will just emit a warning and keep looking for the next
+ *   entry.
  */
-struct dir_iterator *dir_iterator_begin(const char *path);
+struct dir_iterator *dir_iterator_begin(const char *path, int pedantic);
 
 /*
  * Advance the iterator to the first or next item and return ITER_OK.
@@ -76,6 +82,10 @@ struct dir_iterator *dir_iterator_begin(const char *path);
  * dir_iterator and associated resources and return ITER_ERROR. It is
  * a bug to use iterator or call this function again after it has
  * returned ITER_DONE or ITER_ERROR.
+ *
+ * Note that whether dir_iterator_advance will return ITER_ERROR when
+ * failing to fetch the next entry or keep going is defined by the
+ * 'pedantic' option at dir-iterator's initialization.
  */
 int dir_iterator_advance(struct dir_iterator *iterator);
 
diff --git a/refs/files-backend.c b/refs/files-backend.c
index dd8abe9185..c3d3b6c454 100644
--- a/refs/files-backend.c
+++ b/refs/files-backend.c
@@ -2143,7 +2143,7 @@ static struct ref_iterator *reflog_iterator_begin(struct ref_store *ref_store,
 
 	base_ref_iterator_init(ref_iterator, &files_reflog_iterator_vtable, 0);
 	strbuf_addf(&sb, "%s/logs", gitdir);
-	iter->dir_iterator = dir_iterator_begin(sb.buf);
+	iter->dir_iterator = dir_iterator_begin(sb.buf, 0);
 	iter->ref_store = ref_store;
 	strbuf_release(&sb);
 
-- 
2.21.0.rc2.1.g2d5e20a900.dirty