SERVER-69149 Make debug print of SBE expressions more readable

Reapplies the original change with a corrected out-of-bounds
check.

4 files changed, 50 insertions, 25 deletions

diff --git a/jstests/core/column_scan_skip_row_store_projection.js b/jstests/core/column_scan_skip_row_store_projection.js
index 23dcb6b2ae9..97c10f8b3df 100644
--- a/jstests/core/column_scan_skip_row_store_projection.js
+++ b/jstests/core/column_scan_skip_row_store_projection.js
@@ -63,7 +63,7 @@ function test({agg, requiresRowStoreExpr, rowstoreFetches}) {
     const nullRegex =
         /COLUMN_SCAN s.* ((s.*)|(none)) paths\[.*\] pathFilters\[.*\] rowStoreExpr\[\] @.* @.*/;
     const notNullRegex =
-        /COLUMN_SCAN s.* ((s.*)|(none)) paths\[.*\] pathFilters\[.*\] rowStoreExpr\[.*, .*\] @.* @.*/;
+        /COLUMN_SCAN s.* ((s.*)|(none)) paths\[.*\] pathFilters\[.*\] rowStoreExpr\[.*, \n/;
     if (requiresRowStoreExpr) {
         assert(!nullRegex.test(sbeStages), `Don't expect null rowstoreExpr in ${sbeStages}`);
         assert(notNullRegex.test(sbeStages), `Expected non-null rowstoreExpr in ${sbeStages}`);
diff --git a/src/mongo/db/exec/sbe/expressions/expression.cpp b/src/mongo/db/exec/sbe/expressions/expression.cpp
index d337cd8fa14..7176ce3e56a 100644
--- a/src/mongo/db/exec/sbe/expressions/expression.cpp
+++ b/src/mongo/db/exec/sbe/expressions/expression.cpp
@@ -239,6 +239,7 @@ std::vector<DebugPrinter::Block> EPrimBinary::debugPrint() const {
 
     invariant(!hasCollatorArg || isComparisonOp(_op));
 
+    ret.emplace_back("(`");
     DebugPrinter::addBlocks(ret, _nodes[0]->debugPrint());
 
     switch (_op) {
@@ -292,6 +293,7 @@ std::vector<DebugPrinter::Block> EPrimBinary::debugPrint() const {
     }
 
     DebugPrinter::addBlocks(ret, _nodes[1]->debugPrint());
+    ret.emplace_back("`)");
 
     return ret;
 }
@@ -335,7 +337,9 @@ std::vector<DebugPrinter::Block> EPrimUnary::debugPrint() const {
             MONGO_UNREACHABLE;
     }
 
+    ret.emplace_back("`(`");
     DebugPrinter::addBlocks(ret, _nodes[0]->debugPrint());
+    ret.emplace_back("`)");
 
     return ret;
 }
@@ -733,7 +737,7 @@ std::vector<DebugPrinter::Block> EFunction::debugPrint() const {
     std::vector<DebugPrinter::Block> ret;
     DebugPrinter::addKeyword(ret, _name);
 
-    ret.emplace_back("(`");
+    ret.emplace_back("`(`");
     for (size_t idx = 0; idx < _nodes.size(); ++idx) {
         if (idx) {
             ret.emplace_back("`,");
@@ -780,20 +784,24 @@ vm::CodeFragment EIf::compileDirect(CompileCtx& ctx) const {
 
 std::vector<DebugPrinter::Block> EIf::debugPrint() const {
     std::vector<DebugPrinter::Block> ret;
-    DebugPrinter::addKeyword(ret, "if");
 
-    ret.emplace_back("(`");
+    ret.emplace_back(DebugPrinter::Block::cmdIncIndent);
 
     // Print the condition.
+    DebugPrinter::addKeyword(ret, "if");
     DebugPrinter::addBlocks(ret, _nodes[0]->debugPrint());
-    ret.emplace_back("`,");
+    DebugPrinter::addNewLine(ret);
+
     // Print thenBranch.
+    DebugPrinter::addKeyword(ret, "then");
     DebugPrinter::addBlocks(ret, _nodes[1]->debugPrint());
-    ret.emplace_back("`,");
+    DebugPrinter::addNewLine(ret);
+
     // Print elseBranch.
+    DebugPrinter::addKeyword(ret, "else");
     DebugPrinter::addBlocks(ret, _nodes[2]->debugPrint());
 
-    ret.emplace_back("`)");
+    ret.emplace_back(DebugPrinter::Block::cmdDecIndent);
 
     return ret;
 }
@@ -836,22 +844,30 @@ vm::CodeFragment ELocalBind::compileDirect(CompileCtx& ctx) const {
 std::vector<DebugPrinter::Block> ELocalBind::debugPrint() const {
     std::vector<DebugPrinter::Block> ret;
 
-    DebugPrinter::addKeyword(ret, "let");
+    ret.emplace_back(DebugPrinter::Block::cmdIncIndent);
 
+    DebugPrinter::addKeyword(ret, "let");
     ret.emplace_back("[`");
+    ret.emplace_back(DebugPrinter::Block::cmdIncIndent);
+
     for (size_t idx = 0; idx < _nodes.size() - 1; ++idx) {
         if (idx != 0) {
-            ret.emplace_back("`,");
+            DebugPrinter::addNewLine(ret);
         }
 
         DebugPrinter::addIdentifier(ret, _frameId, idx);
         ret.emplace_back("=");
         DebugPrinter::addBlocks(ret, _nodes[idx]->debugPrint());
     }
-    ret.emplace_back("`]");
+    ret.emplace_back(DebugPrinter::Block::cmdDecIndent);
+    ret.emplace_back("]");
+    DebugPrinter::addNewLine(ret);
 
+    DebugPrinter::addKeyword(ret, "in");
     DebugPrinter::addBlocks(ret, _nodes.back()->debugPrint());
 
+    ret.emplace_back(DebugPrinter::Block::cmdDecIndent);
+
     return ret;
 }
 
@@ -896,10 +912,13 @@ vm::CodeFragment ELocalLambda::compileDirect(CompileCtx& ctx) const {
 std::vector<DebugPrinter::Block> ELocalLambda::debugPrint() const {
     std::vector<DebugPrinter::Block> ret;
 
-    DebugPrinter::addKeyword(ret, "\\");
+    DebugPrinter::addKeyword(ret, "lambda");
+    ret.emplace_back("`(`");
     DebugPrinter::addIdentifier(ret, _frameId, 0);
-    ret.emplace_back(".");
+    ret.emplace_back("`)");
+    ret.emplace_back("{");
     DebugPrinter::addBlocks(ret, _nodes.back()->debugPrint());
+    ret.emplace_back("}");
 
     return ret;
 }
@@ -930,11 +949,13 @@ std::vector<DebugPrinter::Block> EFail::debugPrint() const {
     std::vector<DebugPrinter::Block> ret;
     DebugPrinter::addKeyword(ret, "fail");
 
-    ret.emplace_back("(");
+    ret.emplace_back("`(`");
 
     ret.emplace_back(std::to_string(_code));
-    ret.emplace_back(",`");
+    ret.emplace_back("`,");
+    ret.emplace_back("\"`");
     ret.emplace_back(getStringView(_messageTag, _messageVal));
+    ret.emplace_back("`\"`");
 
     ret.emplace_back("`)");
 
diff --git a/src/mongo/db/exec/sbe/stages/union.cpp b/src/mongo/db/exec/sbe/stages/union.cpp
index 2fd6d0b4fc5..9d619f2f505 100644
--- a/src/mongo/db/exec/sbe/stages/union.cpp
+++ b/src/mongo/db/exec/sbe/stages/union.cpp
@@ -27,10 +27,10 @@
  *    it in the license file.
  */
 
-#include "mongo/platform/basic.h"
-
 #include "mongo/db/exec/sbe/stages/union.h"
 
+#include <fmt/format.h>
+
 #include "mongo/db/exec/sbe/expressions/expression.h"
 #include "mongo/db/exec/sbe/size_estimator.h"
 
@@ -197,9 +197,10 @@ std::vector<DebugPrinter::Block> UnionStage::debugPrint() const {
     }
     ret.emplace_back(DebugPrinter::Block("`]"));
 
-    ret.emplace_back(DebugPrinter::Block("[`"));
     ret.emplace_back(DebugPrinter::Block::cmdIncIndent);
     for (size_t childNum = 0; childNum < _children.size(); childNum++) {
+        DebugPrinter::addKeyword(ret, "branch{}"_format(childNum));
+
         ret.emplace_back(DebugPrinter::Block("[`"));
         for (size_t idx = 0; idx < _inputVals[childNum].size(); idx++) {
             if (idx) {
@@ -209,15 +210,11 @@ std::vector<DebugPrinter::Block> UnionStage::debugPrint() const {
         }
         ret.emplace_back(DebugPrinter::Block("`]"));
 
+        ret.emplace_back(DebugPrinter::Block::cmdIncIndent);
         DebugPrinter::addBlocks(ret, _children[childNum]->debugPrint());
-
-        if (childNum + 1 < _children.size()) {
-            ret.emplace_back(DebugPrinter::Block(","));
-            DebugPrinter::addNewLine(ret);
-        }
+        ret.emplace_back(DebugPrinter::Block::cmdDecIndent);
     }
     ret.emplace_back(DebugPrinter::Block::cmdDecIndent);
-    ret.emplace_back(DebugPrinter::Block("`]"));
 
     return ret;
 }
diff --git a/src/mongo/db/exec/sbe/util/debug_print.cpp b/src/mongo/db/exec/sbe/util/debug_print.cpp
index e3d831b5ab5..e33397530fc 100644
--- a/src/mongo/db/exec/sbe/util/debug_print.cpp
+++ b/src/mongo/db/exec/sbe/util/debug_print.cpp
@@ -38,6 +38,7 @@ namespace sbe {
 std::string DebugPrinter::print(const std::vector<Block>& blocks) {
     std::string ret;
     int ident = 0;
+    size_t blockIndex = 0;
     for (auto& b : blocks) {
         bool addSpace = true;
         switch (b.cmd) {
@@ -48,8 +49,13 @@ std::string DebugPrinter::print(const std::vector<Block>& blocks) {
                 break;
             case Block::cmdDecIndent:
                 --ident;
-                ret.append("\n");
-                addIndent(ident, ret);
+                // Avoid unnecessary whitespace if there are multiple adjacent "decrement indent"
+                // tokens.
+                if (blockIndex >= (blocks.size() - 1) ||
+                    blocks[blockIndex + 1].cmd != Block::cmdDecIndent) {
+                    ret.append("\n");
+                    addIndent(ident, ret);
+                }
                 break;
             case Block::cmdNewLine:
                 ret.append("\n");
@@ -111,6 +117,7 @@ std::string DebugPrinter::print(const std::vector<Block>& blocks) {
                 }
             }
         }
+        ++blockIndex;
     }
 
     return ret;