Fix Windows MSVC build failure during ABI generation

CHANGELOG.md

@@ -7,6 +7,11 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Fixed
+
+- Fixed Windows (without WSL) build failure on ABI generation step by adding `/FORCE:UNRESOLVED` linker flag for MSVC
+- Fixed RUSTFLAGS handling in cargo_native::compile to append flags instead of replacing them
+
 ## [0.19.0](https://github.com/near/cargo-near/compare/cargo-near-v0.18.0...cargo-near-v0.19.0) - 2026-01-12
 
 ### Added

cargo-near-build/src/cargo_native/compile.rs

@@ -1,4 +1,4 @@
-use std::{collections::BTreeMap, ffi::OsStr, marker::PhantomData, process::Command, thread};
+use std::{ffi::OsStr, marker::PhantomData, process::Command, thread};
 
 use camino::Utf8Path;
 use cargo_metadata::{Artifact, Message};
@@ -23,9 +23,24 @@ where
     T: ArtifactType,
 {
     let final_env = {
-        let mut env: BTreeMap<_, _> = env.into_iter().collect();
+        // Convert to owned strings to allow modification
+        let mut env: Vec<(String, String)> = env
+            .into_iter()
+            .map(|(k, v)| (k.to_string(), v.to_string()))
+            .collect();
         if hide_warnings {
-            env.insert(crate::env_keys::RUSTFLAGS, "-Awarnings");
+            // Check if RUSTFLAGS already exists and append -Awarnings
+            if let Some(pos) = env
+                .iter()
+                .position(|(k, _)| k == crate::env_keys::RUSTFLAGS)
+            {
+                env[pos].1.push_str(" -Awarnings");
+            } else {
+                env.push((
+                    crate::env_keys::RUSTFLAGS.to_string(),
+                    "-Awarnings".to_string(),
+                ));
+            }
         }
         env
     };
@@ -36,7 +51,7 @@ where
         "build",
         [&["--message-format=json-render-diagnostics"], args].concat(),
         manifest_path.directory().ok(),
-        final_env.iter(),
+        final_env.iter().map(|(k, v)| (k.as_str(), v.as_str())),
         &removed_env,
         color,
     )?;

cargo-near-build/src/near/abi/generate/mod.rs

@@ -70,12 +70,23 @@ pub fn procedure(
     pretty_print::step("Generating ABI");
 
     let compile_env = {
-        let compile_env = vec![
+        #[allow(unused_mut)]
+        let mut compile_env = vec![
             ("CARGO_PROFILE_DEV_OPT_LEVEL", "0"),
             ("CARGO_PROFILE_DEV_DEBUG", "0"),
             ("CARGO_PROFILE_DEV_LTO", "off"),
             (env_keys::BUILD_RS_ABI_STEP_HINT, "true"),
         ];
+
+        // On Windows MSVC, the linker doesn't allow unresolved symbols by default.
+        // When building a dylib for ABI generation, near-sdk's runtime functions
+        // (from near-sys) won't be available since they're provided by the NEAR VM
+        // in wasm builds. We use /FORCE:UNRESOLVED to allow the build to succeed.
+        #[cfg(windows)]
+        {
+            compile_env.push((env_keys::RUSTFLAGS, "-C link-arg=/FORCE:UNRESOLVED"));
+        }
+
         [&compile_env, env].concat()
     };
     let dylib_artifact = cargo_native::compile::run::<Dylib>(