harmony: convert fn names to be valid ts identifiers

In <https://github.com/ollama/ollama/issues/11704#issuecomment-3177380197>
I noticed that hyphens in function names could possibly cause the model
to become confused. Later in that issue I found other explanations, but
at a minimum tool names with spaces in them are confusing to the model
because of the prompt format.

In this change I create a mapper that converts arbitrary tool names into
valid typescript identifiers. It's a little overly strict in that it
doesn't allow all unicode characters that might be valid in ts
identifiers, but it's still very permissive. Since mappings aren't
reversible, we must temporarily store this mapping in order to unmap it
if the model comes back with a call. We also handle the case where
multiple mappings collide into the same mapping and append a counter to
the end to make them unique

server/harmonyparser_test.go

@@ -467,3 +467,71 @@ func TestHarmonyParserStreaming(t *testing.T) {
 		})
 	}
 }
+
+// TestFunctionConvertToValidChars tests only FunctionNameMap.convert(), which doesn't
+// handle any saving (and therefore no dupe handling)
+func TestFunctionConvertToValidChars(t *testing.T) {
+	tests := []struct {
+		name string
+		in   string
+		want string
+	}{
+		{name: "replace spaces with underscores", in: "get weather", want: "get_weather"},
+		{name: "replace hyphens with underscores", in: "get-weather", want: "get_weather"},
+		{name: "replace periods with underscores", in: "get.weather", want: "get_weather"},
+		{name: "disallow non-word characters", in: "get weather!", want: "get_weather"},
+		{name: "strip out invalid non-alphanumeric unicode characters", in: "a🫠bc", want: "abc"},
+		{name: "names that only contain invalid characters", in: "🫠", want: "unnamed"},
+		{name: "leading number", in: "123", want: "_123"},
+		{name: "$ allowed", in: "$", want: "$"},
+		// show that we allow weird unicode letter characters, though we might want
+		// to convert them to their closest ASCII equivalents in the future
+		{name: "allow weird unicode letter characters", in: "𝓸𝓵𝓵𝓪𝓶𝓪", want: "𝓸𝓵𝓵𝓪𝓶𝓪"},
+		// names that look like words but are invalid (i.e., not ID_Start/ID_Continue)
+		{name: "disallow non-word characters that look like words", in: "ⓞⓛⓛⓐⓜⓐ123", want: "_123"},
+	}
+
+	for i, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			parser := NewFunctionNameMap()
+			got := parser.convertToValidChars(tt.in)
+			if got != tt.want {
+				t.Errorf("case %d: got %q, want %q", i, got, tt.want)
+			}
+		})
+	}
+}
+
+func TestFunctionConvertAndAdd(t *testing.T) {
+	// make a fresh map for each test, but within a test use the same map so we can test for dupe handling
+	tests := []struct {
+		name string
+		in   []string
+		want []string
+	}{
+		{name: "basic dupe handling", in: []string{"get weather", "get weather"}, want: []string{"get_weather", "get_weather_2"}},
+		{name: "dupes from different user-specified names", in: []string{"get weather", "get_weather", "get-weather"}, want: []string{"get_weather", "get_weather_2", "get_weather_3"}},
+		{name: "non dupes after dupes", in: []string{"get weather", "get_weather", "get-weather", "something-different"}, want: []string{"get_weather", "get_weather_2", "get_weather_3", "something_different"}},
+		{name: "multiple sets of dupes", in: []string{"a", "a", "b", "a", "a", "b", "a"}, want: []string{"a", "a_2", "b", "a_3", "a_4", "b_2", "a_5"}},
+	}
+
+	for i, tt := range tests {
+		parser := NewFunctionNameMap()
+		t.Run(tt.name, func(t *testing.T) {
+			for j, in := range tt.in {
+				got := parser.ConvertAndAdd(in)
+				want := tt.want[j]
+				if got != want {
+					t.Errorf("case %d: got %q, want %q", i, got, want)
+				}
+				// check that the maps are correct
+				if parser.userToHarmony[in] != want {
+					t.Errorf("case %d: userToHarmony[%q] = %q, want %q", i, in, parser.userToHarmony[in], want)
+				}
+				if parser.harmonyToUser[want] != in {
+					t.Errorf("case %d: harmonyToUser[%q] = %q, want %q", i, want, parser.harmonyToUser[want], in)
+				}
+			}
+		})
+	}
+}