From b540c2419f2974780e0bff3d04a767248b90451f Mon Sep 17 00:00:00 2001
From: Sergei Zimmerman <xokdvium@proton.me>
Date: Thu, 13 Mar 2025 12:55:39 +0000
Subject: [PATCH] {libutil,libexpr}: Move pos-idx,pos-table code to libutil

All of this code doesn't actually depend on anything from
libexpr. Because Pos is so tigtly coupled with Error, it
makes sense to have in the same library.

(cherry picked from commit a53b184e63114ec390e3a1b1f7cd45b8a012ab04)
---
 maintainers/flake-module.nix          |  1 -
 src/libexpr/meson.build               |  2 --
 src/libexpr/nixexpr.cc                | 35 -------------------------
 src/libutil/meson.build               |  3 +++
 src/{libexpr => libutil}/pos-idx.hh   |  1 +
 src/libutil/pos-table.cc              | 37 +++++++++++++++++++++++++++
 src/{libexpr => libutil}/pos-table.hh | 10 +++++---
 7 files changed, 48 insertions(+), 41 deletions(-)
 rename src/{libexpr => libutil}/pos-idx.hh (98%)
 create mode 100644 src/libutil/pos-table.cc
 rename src/{libexpr => libutil}/pos-table.hh (94%)

diff --git a/maintainers/flake-module.nix b/maintainers/flake-module.nix
index 4d504b8ee..f18e9b41e 100644
--- a/maintainers/flake-module.nix
+++ b/maintainers/flake-module.nix
@@ -127,7 +127,6 @@
               ''^src/libexpr/nixexpr\.cc$''
               ''^src/libexpr/nixexpr\.hh$''
               ''^src/libexpr/parser-state\.hh$''
-              ''^src/libexpr/pos-table\.hh$''
               ''^src/libexpr/primops\.cc$''
               ''^src/libexpr/primops\.hh$''
               ''^src/libexpr/primops/context\.cc$''
diff --git a/src/libexpr/meson.build b/src/libexpr/meson.build
index 987300d58..dffcc1742 100644
--- a/src/libexpr/meson.build
+++ b/src/libexpr/meson.build
@@ -172,8 +172,6 @@ headers = [config_h] + files(
   # internal: 'lexer-helpers.hh',
   'nixexpr.hh',
   'parser-state.hh',
-  'pos-idx.hh',
-  'pos-table.hh',
   'primops.hh',
   'print-ambiguous.hh',
   'print-options.hh',
diff --git a/src/libexpr/nixexpr.cc b/src/libexpr/nixexpr.cc
index e8bd02b9b..f17226728 100644
--- a/src/libexpr/nixexpr.cc
+++ b/src/libexpr/nixexpr.cc
@@ -601,41 +601,6 @@ void ExprLambda::setDocComment(DocComment docComment) {
     }
 };
 
-
-
-/* Position table. */
-
-Pos PosTable::operator[](PosIdx p) const
-{
-    auto origin = resolve(p);
-    if (!origin)
-        return {};
-
-    const auto offset = origin->offsetOf(p);
-
-    Pos result{0, 0, origin->origin};
-    auto lines = this->lines.lock();
-    auto linesForInput = (*lines)[origin->offset];
-
-    if (linesForInput.empty()) {
-        auto source = result.getSource().value_or("");
-        const char * begin = source.data();
-        for (Pos::LinesIterator it(source), end; it != end; it++)
-            linesForInput.push_back(it->data() - begin);
-        if (linesForInput.empty())
-            linesForInput.push_back(0);
-    }
-    // as above: the first line starts at byte 0 and is always present
-    auto lineStartOffset = std::prev(
-        std::upper_bound(linesForInput.begin(), linesForInput.end(), offset));
-
-    result.line = 1 + (lineStartOffset - linesForInput.begin());
-    result.column = 1 + (offset - *lineStartOffset);
-    return result;
-}
-
-
-
 /* Symbol table. */
 
 size_t SymbolTable::totalSize() const
diff --git a/src/libutil/meson.build b/src/libutil/meson.build
index df459f0e5..9e70d0549 100644
--- a/src/libutil/meson.build
+++ b/src/libutil/meson.build
@@ -155,6 +155,7 @@ sources = files(
   'memory-source-accessor.cc',
   'mounted-source-accessor.cc',
   'position.cc',
+  'pos-table.cc',
   'posix-source-accessor.cc',
   'references.cc',
   'serialise.cc',
@@ -225,6 +226,8 @@ headers = [config_h] + files(
   'muxable-pipe.hh',
   'os-string.hh',
   'pool.hh',
+  'pos-idx.hh',
+  'pos-table.hh',
   'position.hh',
   'posix-source-accessor.hh',
   'processes.hh',
diff --git a/src/libexpr/pos-idx.hh b/src/libutil/pos-idx.hh
similarity index 98%
rename from src/libexpr/pos-idx.hh
rename to src/libutil/pos-idx.hh
index 2faa6b7fe..c1749ba69 100644
--- a/src/libexpr/pos-idx.hh
+++ b/src/libutil/pos-idx.hh
@@ -1,4 +1,5 @@
 #pragma once
+///@file
 
 #include <cinttypes>
 #include <functional>
diff --git a/src/libutil/pos-table.cc b/src/libutil/pos-table.cc
new file mode 100644
index 000000000..8178beb90
--- /dev/null
+++ b/src/libutil/pos-table.cc
@@ -0,0 +1,37 @@
+#include "pos-table.hh"
+
+#include <algorithm>
+
+namespace nix {
+
+/* Position table. */
+
+Pos PosTable::operator[](PosIdx p) const
+{
+    auto origin = resolve(p);
+    if (!origin)
+        return {};
+
+    const auto offset = origin->offsetOf(p);
+
+    Pos result{0, 0, origin->origin};
+    auto lines = this->lines.lock();
+    auto linesForInput = (*lines)[origin->offset];
+
+    if (linesForInput.empty()) {
+        auto source = result.getSource().value_or("");
+        const char * begin = source.data();
+        for (Pos::LinesIterator it(source), end; it != end; it++)
+            linesForInput.push_back(it->data() - begin);
+        if (linesForInput.empty())
+            linesForInput.push_back(0);
+    }
+    // as above: the first line starts at byte 0 and is always present
+    auto lineStartOffset = std::prev(std::upper_bound(linesForInput.begin(), linesForInput.end(), offset));
+
+    result.line = 1 + (lineStartOffset - linesForInput.begin());
+    result.column = 1 + (offset - *lineStartOffset);
+    return result;
+}
+
+}
diff --git a/src/libexpr/pos-table.hh b/src/libutil/pos-table.hh
similarity index 94%
rename from src/libexpr/pos-table.hh
rename to src/libutil/pos-table.hh
index ba2b91cf3..673cf62ae 100644
--- a/src/libexpr/pos-table.hh
+++ b/src/libutil/pos-table.hh
@@ -1,4 +1,5 @@
 #pragma once
+///@file
 
 #include <cstdint>
 #include <vector>
@@ -18,9 +19,12 @@ public:
     private:
         uint32_t offset;
 
-        Origin(Pos::Origin origin, uint32_t offset, size_t size):
-            offset(offset), origin(origin), size(size)
-        {}
+        Origin(Pos::Origin origin, uint32_t offset, size_t size)
+            : offset(offset)
+            , origin(origin)
+            , size(size)
+        {
+        }
 
     public:
         const Pos::Origin origin;