Fix typing with exact match mode on and auto select

1. require auto select to only select when code is fully matched.
   Certain table's prefix has only one match, since the code is defined
   as the longer version, we should always require auto select to match
   the full code. Otherwise, user may always update the table to make
   that a short code.
2. When exact matching mode is on, we need to indeed check if it is the
   only match, otherwise certain code may not be possible to be typed.

Fix fcitx/fcitx5-chinese-addons#150

src/libime/table/tablebaseddictionary.cpp

@@ -1324,17 +1324,18 @@ bool TableBasedDictionary::hasMatchingWords(std::string_view code) const {
 }
 
 bool TableBasedDictionary::hasOneMatchingWord(std::string_view code) const {
-    bool hasMatch = false;
+    bool hasOneMatch = false;
     matchWords(
         code, TableMatchMode::Prefix,
-        [&hasMatch](std::string_view, std::string_view, uint32_t, PhraseFlag) {
-            if (hasMatch) {
+        [&hasOneMatch](std::string_view, std::string_view, uint32_t, PhraseFlag) {
+            if (hasOneMatch) {
+                hasOneMatch = false;
                 return false;
             }
-            hasMatch = true;
+            hasOneMatch = true;
             return true;
         });
-    return hasMatch;
+    return hasOneMatch;
 }
 
 PhraseFlag TableBasedDictionary::wordExists(std::string_view code,

src/libime/table/tablecontext.cpp

@@ -173,7 +173,17 @@ class TableContextPrivate : public fcitx::QPtrHolder<TableContext> {
         if (!canDoAutoSelect()) {
             return false;
         }
-        return candidates_.size() == 1;
+        if (candidates_.size() != 1) {
+            return false;
+        }
+
+        if (candidates_[0].sentence().size() != 1) {
+            return false;
+        }
+        FCITX_Q();
+        return q->code(candidates_[0]) == q->currentCode() &&
+               (!dict_.tableOptions().exactMatch() ||
+                dict_.hasOneMatchingWord(q->currentCode()));
     };
 
     State currentState() {