Preserve type of strings that look like numbers when emitting YAML

Fixes Cantera#1610

src/base/AnyMap.cpp

@@ -283,10 +283,15 @@ YAML::Emitter& operator<<(YAML::Emitter& out, const AnyMap& rhs)
         for (const auto& [name, value] : rhs.ordered()) {
             string valueStr;
             bool foundType = true;
+            bool needsQuotes = false;
             if (value.is<double>()) {
                 valueStr = formatDouble(value.asDouble(), getPrecision(value));
             } else if (value.is<string>()) {
                 valueStr = value.asString();
+                if (isFloat(valueStr)) {
+                    // Quote strings that look like numbers to preserve their type
+                    needsQuotes = true;
+                }
             } else if (value.is<long int>()) {
                 valueStr = fmt::format("{}", value.asInt());
             } else if (value.is<bool>()) {
@@ -303,6 +308,9 @@ YAML::Emitter& operator<<(YAML::Emitter& out, const AnyMap& rhs)
                     width = 15;
                 }
                 out << name;
+                if (needsQuotes) {
+                    out << YAML::SingleQuoted;
+                }
                 out << valueStr;
                 width += name.size() + valueStr.size() + 4;
             } else {
@@ -327,6 +335,9 @@ YAML::Emitter& operator<<(YAML::Emitter& out, const AnyMap& rhs)
 //! Write YAML strings spanning multiple lines if input includes endline '\n'
 void emitString(YAML::Emitter& out, const string& str0) {
     if (str0.rfind('\n') == string::npos) {
+        if (isFloat(str0)) {
+            out << YAML::SingleQuoted;
+        }
         out << str0;
         return;
     }
@@ -360,6 +371,30 @@ void emitFlowVector(YAML::Emitter& out, const vector<double>& v, long int precis
     out << YAML::EndSeq;
 }
 
+//! Write a vector in YAML "flow" style, wrapping lines to avoid exceeding the
+//! preferred maximum line length (set by `max_line_length`). Specialized for
+//! `vector<string>` to quote strings that look like numeric values
+void emitFlowVector(YAML::Emitter& out, const vector<string>& v)
+{
+    out << YAML::Flow;
+    out << YAML::BeginSeq;
+    size_t width = 15; // wild guess, but no better value is available
+    for (const string& x : v) {
+        // Wrap to the next line if this item would exceed the target line length
+        if (width + x.size() > max_line_length) {
+            out << YAML::Newline;
+            width = 15;
+        }
+        if (isFloat(x)) {
+            out << SingleQuoted;
+            width += 2;
+        }
+        out << x;
+        width += x.size() + 2;
+    }
+    out << YAML::EndSeq;
+}
+
 //! Write a vector in YAML "flow" style, wrapping lines to avoid exceeding the
 //! preferred maximum line length (set by `max_line_length`).
 template <typename T>

test/python/test_composite.py

@@ -1222,8 +1222,14 @@ def test_yaml_strings(self):
         gas = ct.Solution('h2o2.yaml', transport_model=None)
         desc = "   Line 1\n    Line 2\n  Line 3"
         note = "First\n\nSecond\n  Third"
+        note2 = "123199"  # scalar string
+        note3 = ["77", "888", "9"]  # list with all strings
+        note4 = ["111213", 444, "5.10"]  # mixed types
         gas.update_user_header({"description": desc})
-        gas.species(2).update_user_data({"note": note})
+        gas.species(1).update_user_data({"note": note})
+        gas.species(2).update_user_data({"note": note2})
+        gas.species(3).update_user_data({"note": note3})
+        gas.species(4).update_user_data({"note": note4})
 
         gas.write_yaml(self.test_work_path / "h2o2-generated-user-header.yaml")
         gas2 = ct.Solution(self.test_work_path / "h2o2-generated-user-header.yaml")
@@ -1232,7 +1238,12 @@ def test_yaml_strings(self):
         # (element annotated with '|-' instead of just '|') but this doesn't seem to be
         # possible as of yaml-cpp 0.8.0.
         assert gas2.input_header["description"].strip() == desc.strip()
-        assert gas2.species(2).input_data["note"].strip() == note.strip()
+        assert gas2.species(1).input_data["note"].strip() == note.strip()
+
+        # number-like strings should be preserved as strings
+        assert gas2.species(2).input_data["note"] == note2
+        assert gas2.species(3).input_data["note"] == note3
+        assert gas2.species(4).input_data["note"] == note4
 
 
 class TestSpeciesSerialization(utilities.CanteraTest):