From eee5400b7dc37845ea5f42e0841320953e7852b2 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Carl=20=C3=85stholm?= <carl@astholm.se>
Date: Fri, 15 Mar 2024 19:59:02 +0100
Subject: [PATCH] Account for dependency boundaries when duping headers

This is a temporary workaround that can be revered if/when 'path'
lazy paths are updated to encode which build root they are relative to.
---
 lib/std/Build/Step/Compile.zig            | 31 ++++++++++++++++++++---
 test/standalone/install_headers/build.zig |  4 +--
 2 files changed, 29 insertions(+), 6 deletions(-)

diff --git a/lib/std/Build/Step/Compile.zig b/lib/std/Build/Step/Compile.zig
index 2883992c73..4a5364176a 100644
--- a/lib/std/Build/Step/Compile.zig
+++ b/lib/std/Build/Step/Compile.zig
@@ -264,8 +264,20 @@ pub const HeaderInstallation = union(enum) {
         dest_rel_path: []const u8,
 
         pub fn dupe(self: File, b: *std.Build) File {
+            // 'path' lazy paths are relative to the build root of some step, inferred from the step
+            // in which they are used. This means that we can't dupe such paths, because they may
+            // come from dependencies with their own build roots and duping the paths as is might
+            // cause the build script to search for the file relative to the wrong root.
+            // As a temporary workaround, we convert build root-relative paths to absolute paths.
+            // If/when the build-root relative paths are updated to encode which build root they are
+            // relative to, this workaround should be removed.
+            const duped_source: LazyPath = switch (self.source) {
+                .path => |root_rel| .{ .cwd_relative = b.pathFromRoot(root_rel) },
+                else => self.source.dupe(b),
+            };
+
             return .{
-                .source = self.source.dupe(b),
+                .source = duped_source,
                 .dest_rel_path = b.dupePath(self.dest_rel_path),
             };
         }
@@ -293,8 +305,20 @@ pub const HeaderInstallation = union(enum) {
         };
 
         pub fn dupe(self: Directory, b: *std.Build) Directory {
+            // 'path' lazy paths are relative to the build root of some step, inferred from the step
+            // in which they are used. This means that we can't dupe such paths, because they may
+            // come from dependencies with their own build roots and duping the paths as is might
+            // cause the build script to search for the file relative to the wrong root.
+            // As a temporary workaround, we convert build root-relative paths to absolute paths.
+            // If/when the build-root relative paths are updated to encode which build root they are
+            // relative to, this workaround should be removed.
+            const duped_source: LazyPath = switch (self.source) {
+                .path => |root_rel| .{ .cwd_relative = b.pathFromRoot(root_rel) },
+                else => self.source.dupe(b),
+            };
+
             return .{
-                .source = self.source.dupe(b),
+                .source = duped_source,
                 .dest_rel_path = b.dupePath(self.dest_rel_path),
                 .options = self.options.dupe(b),
             };
@@ -492,9 +516,8 @@ pub fn installConfigHeader(cs: *Compile, config_header: *Step.ConfigHeader) void
 /// module's include search path.
 pub fn installLibraryHeaders(cs: *Compile, lib: *Compile) void {
     assert(lib.kind == .lib);
-    const b = cs.step.owner;
     for (lib.installed_headers.items) |installation| {
-        const installation_copy = installation.dupe(b);
+        const installation_copy = installation.dupe(lib.step.owner);
         cs.installed_headers.append(installation_copy) catch @panic("OOM");
         cs.addHeaderInstallationToIncludeTree(installation_copy);
         installation_copy.getSource().addStepDependencies(&cs.step);
diff --git a/test/standalone/install_headers/build.zig b/test/standalone/install_headers/build.zig
index 965239aac5..4c9bbb501a 100644
--- a/test/standalone/install_headers/build.zig
+++ b/test/standalone/install_headers/build.zig
@@ -70,7 +70,7 @@ pub fn build(b: *std.Build) void {
     run_exe.expectStdOutEqual("ABD12X");
     test_step.dependOn(&run_exe.step);
 
-    const install_exe = b.addInstallArtifact(libfoo, .{
+    const install_libfoo = b.addInstallArtifact(libfoo, .{
         .dest_dir = .{ .override = .{ .custom = "custom" } },
         .h_dir = .{ .override = .{ .custom = "custom/include" } },
         .implib_dir = .disabled,
@@ -94,6 +94,6 @@ pub fn build(b: *std.Build) void {
     });
     run_check_exists.setCwd(.{ .cwd_relative = b.getInstallPath(.prefix, "") });
     run_check_exists.expectExitCode(0);
-    run_check_exists.step.dependOn(&install_exe.step);
+    run_check_exists.step.dependOn(&install_libfoo.step);
     test_step.dependOn(&run_check_exists.step);
 }