truffle(test): modify runInREPL submit command

Currently runInREPL sends all queued commands to the child process on
the first detected REPL prompt and closes the input stream on the
second REPL prompt detection which terminates the child process (bad).

This PR reworks the logic to send one queued command per REPL prompt.

packages/truffle/test/scenarios/commandRunner.js

@@ -60,11 +60,16 @@ module.exports = {
         ? `debug(${displayHost})>`
         : `truffle(${displayHost})>`;
 
-    let seenChildPrompt = false;
+    // seems safe to escape parens only, as the readyprompt is constructed from
+    // [a-zA-Z] strings and wrapping parens.
+    const escapedPrompt = readyPrompt.replace("(", "\\(").replace(")", "\\)");
+    const readyPromptRex = new RegExp(`^${escapedPrompt}`, "gm");
+
     let outputBuffer = "";
 
     return new Promise((resolve, reject) => {
       const child = exec(cmdLine, { cwd: config.working_directory });
+      let numSeenPrompts = 0;
 
       if (child.error) return reject(child.error);
 
@@ -74,17 +79,20 @@ module.exports = {
 
       child.stdout.on("data", data => {
         // accumulate buffer from chunks
-        if (!seenChildPrompt) {
-          outputBuffer += data;
-        }
+        outputBuffer += data;
 
-        // child process is ready for input when it displays the readyPrompt
-        if (!seenChildPrompt && outputBuffer.includes(readyPrompt)) {
-          seenChildPrompt = true;
-          inputCommands.forEach(command => {
-            child.stdin.write(command + EOL);
-          });
-          child.stdin.end();
+        // count prompt
+        const foundPrompts = (outputBuffer.match(readyPromptRex) || []).length;
+        if (foundPrompts > numSeenPrompts) {
+          numSeenPrompts++;
+          if (inputCommands.length === 0) {
+            // commands exhausted, close stdin
+            child.stdin.end();
+          } else {
+            // fifo pop next command and submit
+            const nextCmd = inputCommands.shift();
+            child.stdin.write(nextCmd + EOL);
+          }
         }
 
         config.logger.log("OUT: ", data);