Skip non-string metadata.json entries instead of reading them as strings

dirmeta2tmp() warned about a metadata entry that was not a string/string
pair and then read it as a string anyway. Under the new type-tagged
accessors that trips the assert in json_object::string(); before them it
reinterpreted the node's storage as a char pointer, which segfaulted for
most values. Either way, tippecanoe-decode and tile-join could not read a
directory tileset whose metadata.json had a numeric minzoom or a nested
object, which is common in metadata.json files written by other tools.

Add the missing continue, and cover it in raw-tiles-test.

pmtilesmeta2tmp() handles the same case correctly but read the key with
string() before its own JSON_STRING check, so the assert would have fired
ahead of the check meant to catch a bad key. Hoist the check above the
read. The parser rejects non-string hash keys, so this is unreachable in
practice; the ordering is what makes the check meaningful.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017KNxyHKasyWrWcvre2yK4r

Makefile

@@ -261,6 +261,14 @@ raw-tiles-test: tippecanoe tippecanoe-decode tile-join
 	./tippecanoe-decode -x generator tests/raw-tiles/nothing > tests/raw-tiles/nothing.json.check
 	cmp tests/raw-tiles/nothing.json.check tests/raw-tiles/nothing.json
 	rm -r tests/raw-tiles/nothing tests/raw-tiles/nothing.json.check
+	# Test that a non-string value in metadata.json is reported and skipped
+	# instead of being read as a string (which used to crash)
+	./tippecanoe -q -f -e tests/raw-tiles/nonstring tests/raw-tiles/hackspots.geojson
+	sed -i.bak 's/"minzoom": "0"/"minzoom": 0/' tests/raw-tiles/nonstring/metadata.json
+	rm tests/raw-tiles/nonstring/metadata.json.bak
+	grep -q '"minzoom": 0' tests/raw-tiles/nonstring/metadata.json
+	./tippecanoe-decode -x generator tests/raw-tiles/nonstring > /dev/null
+	rm -r tests/raw-tiles/nonstring
 
 pmtiles-test: tippecanoe tippecanoe-decode tile-join
 	./tippecanoe -q -f -o tests/pmtiles/hackspots.pmtiles -r1 -pC tests/raw-tiles/hackspots.geojson

dirtiles.cpp

@@ -261,8 +261,15 @@ sqlite3 *dirmeta2tmp(const char *fname) {
 		}
 
 		for (const auto &e : o->entries()) {
+			// Skip, rather than just warn about, anything that isn't a
+			// string/string pair: reading a non-string through string()
+			// would assert in a debug build and misinterpret the node's
+			// storage in a release build. (A metadata.json written by
+			// something other than tippecanoe may well have numeric
+			// minzoom/maxzoom or a nested "json" object.)
 			if (e.key->type != JSON_STRING || e.value->type != JSON_STRING) {
 				fprintf(stderr, "%s: non-string in metadata\n", name.c_str());
+				continue;
 			}
 
 			char *sql = sqlite3_mprintf("INSERT INTO metadata (name, value) VALUES (%Q, %Q);", e.key->string().c_str(), e.value->string().c_str());

pmtiles_file.cpp

@@ -416,6 +416,16 @@ sqlite3 *pmtilesmeta2tmp(const char *fname, const char *pmtiles_map) {
 	state.json_write_hash();
 
 	for (const auto &e : o->entries()) {
+		// Establish that the key really is a string before reading it as
+		// one, rather than after: string() asserts on the type, so the
+		// check has to come first to be the thing that catches a bad key.
+		// (The parser rejects non-string hash keys, so this is belt and
+		// braces, but the ordering is what makes it meaningful.)
+		if (e.key->type != JSON_STRING) {
+			fprintf(stderr, "%s: non-string key in metadata\n", fname);
+			continue;
+		}
+
 		const std::string &key = e.key->string();
 		if (key == "vector_layers" && e.value->type == JSON_ARRAY) {
 			has_json = true;
@@ -441,7 +451,7 @@ sqlite3 *pmtilesmeta2tmp(const char *fname, const char *pmtiles_map) {
 				fprintf(stderr, "set %s in metadata: %s\n", key.c_str(), err);
 			}
 			sqlite3_free(sql);
-		} else if (e.key->type != JSON_STRING || e.value->type != JSON_STRING) {
+		} else if (e.value->type != JSON_STRING) {
 			fprintf(stderr, "%s\n", key.c_str());
 			fprintf(stderr, "%s: non-string in metadata\n", fname);
 		} else {