feat: Add automatic .csproj/.fsproj project scanning and Bazel target generation

.bazelci/presubmit.yml

@@ -19,7 +19,16 @@ matrix:
       ["--@rules_dotnet//dotnet/settings:strict_deps=true"],
       ["--@rules_dotnet//dotnet/settings:strict_deps=false"],
     ]
-  e2e_working_directory: ["e2e/net8.0", "e2e/net9.0", "e2e/net10.0", "e2e/web_sdk"]
+  e2e_working_directory:
+    [
+      "e2e/dotnet_projects_net8.0",
+      "e2e/dotnet_projects_net9.0",
+      "e2e/dotnet_projects_net10.0",
+      "e2e/net8.0",
+      "e2e/net9.0",
+      "e2e/net10.0",
+      "e2e/web_sdk",
+    ]
 
 tasks:
   test_all:

MODULE.bazel

@@ -44,6 +44,7 @@ bazel_dep(name = "bazel_skylib", version = "1.7.1")
 bazel_dep(name = "platforms", version = "1.0.0")
 bazel_dep(name = "bazel_lib", version = "3.0.0")
 bazel_dep(name = "rules_shell", version = "0.5.0")
+bazel_dep(name = "xml.bzl", version = "0.2.2")
 
 # Dev dependencies
 bazel_dep(name = "rules_pkg", version = "1.1.0", dev_dependency = True)

dotnet/BUILD.bazel

@@ -35,6 +35,7 @@ bzl_library(
         "//dotnet/private/rules/csharp:library",
         "//dotnet/private/rules/csharp:nunit_test",
         "//dotnet/private/rules/csharp:test",
+        "//dotnet/private/rules/dotnet_projects:generated_props",
         "//dotnet/private/rules/fsharp:binary",
         "//dotnet/private/rules/fsharp:library",
         "//dotnet/private/rules/fsharp:nunit_test",
@@ -84,7 +85,11 @@ bzl_library(
     name = "extensions",
     srcs = ["extensions.bzl"],
     visibility = ["//visibility:public"],
-    deps = [":repositories"],
+    deps = [
+        ":repositories",
+        "//dotnet/private/rules/dotnet_projects:dotnet_projects_repo",
+        "//dotnet/private/rules/dotnet_projects:tfm_utils",
+    ],
 )
 
 bzl_library(

dotnet/defs.bzl

@@ -19,6 +19,11 @@ load(
     "//dotnet/private/rules/csharp:test.bzl",
     _csharp_test = "csharp_test",
 )
+load(
+    "//dotnet/private/rules/dotnet_projects:generated_props.bzl",
+    _dotnet_generated_props = "dotnet_generated_props",
+    _dotnet_generated_props_test = "dotnet_generated_props_test",
+)
 load(
     "//dotnet/private/rules/fsharp:binary.bzl",
     _fsharp_binary = "fsharp_binary",
@@ -71,3 +76,5 @@ import_dll = _import_dll
 nuget_repo = _nuget_repo
 nuget_archive = _nuget_archive
 dotnet_tool = _dotnet_tool
+dotnet_generated_props = _dotnet_generated_props
+dotnet_generated_props_test = _dotnet_generated_props_test

dotnet/extensions.bzl

@@ -1,10 +1,12 @@
 "extensions for bzlmod"
 
+load("//dotnet/private/rules/dotnet_projects:dotnet_projects_repo.bzl", "dotnet_projects_repo")
 load(":repositories.bzl", "dotnet_register_toolchains")
 
 _DEFAULT_NAME = "dotnet"
 
-_ATTRS = {
+# buildifier: disable=unsorted-dict-items
+_TOOLCHAIN_ATTRS = {
     "name": attr.string(
         doc = "Base name for generated repositories",
         default = _DEFAULT_NAME,
@@ -14,7 +16,36 @@ _ATTRS = {
     ),
 }
 
+# buildifier: disable=unsorted-dict-items
+_SCAN_PROJECTS_ATTRS = {
+    "exclude_patterns": attr.string_list(
+        doc = """Glob patterns for paths to exclude from scanning.
+
+Default patterns exclude bin/, obj/, .git/, .jj/, and bazel-* directories.""",
+    ),
+    "nuget_repo_name": attr.string(
+        default = "dotnet_projects.nuget",
+        doc = """Name of the NuGet repository to generate.
+
+Packages can be referenced as @{nuget_repo_name}//PackageName.""",
+    ),
+    "auto_register_toolchains": attr.bool(
+        default = False,
+        doc = """If true, automatically register toolchains for discovered TFMs.
+
+When enabled, the extension will analyze target frameworks from all discovered
+.csproj/.fsproj files and register any missing toolchains needed to build them.""",
+    ),
+    "fail_on_missing_toolchain": attr.bool(
+        default = True,
+        doc = """If true, fail when a project targets a TFM not covered by registered toolchains.
+
+Set to false to only emit warnings instead of failing.""",
+    ),
+}
+
 def _toolchain_extension(module_ctx):
+    # Collect registered toolchains
     registrations = {}
     for mod in module_ctx.modules:
         for toolchain in mod.tags.toolchain:
@@ -33,16 +64,97 @@ def _toolchain_extension(module_ctx):
                 ))
             else:
                 registrations[toolchain.name] = toolchain.dotnet_version
+
+    # Collect scan_projects configuration
+    scan_config = None
+    for mod in module_ctx.modules:
+        for config in mod.tags.scan_projects:
+            if scan_config != None:
+                # Only use first scan_projects configuration (from root module)
+                continue
+            scan_config = config
+
+    # Register toolchains
     for name, dotnet_version in registrations.items():
         dotnet_register_toolchains(
             name = name,
             dotnet_version = dotnet_version,
             register = False,
         )
 
+    # Handle project scanning if enabled
+    repos_to_return = []
+    if scan_config != None:
+        # Configure exclude patterns
+        exclude_patterns = ["**/bin/**", "**/obj/**", "**/.git/**", "**/.jj/**", "**/bazel-*/**"]
+        if scan_config.exclude_patterns:
+            exclude_patterns = exclude_patterns + list(scan_config.exclude_patterns)
+
+        nuget_repo_name = scan_config.nuget_repo_name if scan_config.nuget_repo_name else "dotnet_projects.nuget"
+
+        # Create the csproj repository
+        # The repository rule will use @@//:MODULE.bazel to find the workspace root
+        dotnet_projects_repo(
+            name = "dotnet_projects",
+            exclude_patterns = exclude_patterns,
+            nuget_repo_name = nuget_repo_name,
+            # Pass registered toolchains for validation
+            registered_toolchains = json.encode(registrations),
+            auto_register_toolchains = scan_config.auto_register_toolchains,
+            fail_on_missing_toolchain = scan_config.fail_on_missing_toolchain,
+        )
+        repos_to_return.append("dotnet_projects")
+
+    return module_ctx.extension_metadata(
+        reproducible = False if scan_config else True,
+        root_module_direct_deps = repos_to_return if repos_to_return else "all",
+        root_module_direct_dev_deps = [],
+    )
+
 dotnet = module_extension(
     implementation = _toolchain_extension,
+    # buildifier: disable=unsorted-dict-items
     tag_classes = {
-        "toolchain": tag_class(attrs = _ATTRS),
+        "toolchain": tag_class(attrs = _TOOLCHAIN_ATTRS),
+        "scan_projects": tag_class(
+            attrs = _SCAN_PROJECTS_ATTRS,
+            doc = """Enable automatic scanning of .csproj and .fsproj files.
+
+When enabled, the extension will:
+1. Scan the workspace for .csproj and .fsproj files
+2. Parse each file to extract properties, sources, and dependencies
+3. Generate a @dotnet_projects repository with .bzl files for each project
+4. Validate that registered toolchains cover all discovered target frameworks
+
+Usage in MODULE.bazel:
+    dotnet = use_extension("@rules_dotnet//dotnet:extensions.bzl", "dotnet")
+    dotnet.toolchain(dotnet_version = "10.0.100")
+    dotnet.scan_projects()
+    use_repo(dotnet, "dotnet_toolchains", "dotnet_projects")
+
+Usage in BUILD files:
+    load("@dotnet_projects//path/to:MyProject.csproj.bzl", "auto_dotnet_targets")
+    auto_dotnet_targets(name = "MyProject")
+
+File Change Detection:
+    Changes to existing .csproj/.fsproj files are automatically detected.
+    New files in existing project directories are also detected.
+
+    However, new project files in entirely new directories require manual sync:
+        bazel sync --only=@dotnet_projects
+
+Requirements:
+    Bazel 7.1 or later is required for the scan_projects feature.
+""",
+        ),
     },
+    doc = """Extension for .NET toolchains and project scanning.
+
+This extension provides two main features:
+1. Toolchain registration via dotnet.toolchain()
+2. Project scanning via dotnet.scan_projects()
+
+The extension will validate that registered toolchains can build all discovered
+target frameworks, and optionally auto-register missing toolchains.
+""",
 )

dotnet/private/rules/dotnet_projects/BUILD.bazel

@@ -0,0 +1,55 @@
+load("@bazel_skylib//:bzl_library.bzl", "bzl_library")
+
+bzl_library(
+    name = "parser",
+    srcs = ["parser.bzl"],
+    visibility = ["//dotnet:__subpackages__"],
+    deps = [
+        "@xml.bzl//:xml",
+    ],
+)
+
+bzl_library(
+    name = "nuget_collector",
+    srcs = ["nuget_collector.bzl"],
+    visibility = ["//dotnet:__subpackages__"],
+)
+
+bzl_library(
+    name = "generator",
+    srcs = ["generator.bzl"],
+    visibility = ["//dotnet:__subpackages__"],
+    deps = [
+        ":parser",
+        "@bazel_skylib//lib:paths",
+    ],
+)
+
+bzl_library(
+    name = "tfm_utils",
+    srcs = ["tfm_utils.bzl"],
+    visibility = ["//dotnet:__subpackages__"],
+)
+
+bzl_library(
+    name = "dotnet_projects_repo",
+    srcs = ["dotnet_projects_repo.bzl"],
+    visibility = ["//dotnet:__subpackages__"],
+    deps = [
+        ":generator",
+        ":nuget_collector",
+        ":parser",
+        ":tfm_utils",
+        "@bazel_lib//lib:glob_match",
+    ],
+)
+
+bzl_library(
+    name = "generated_props",
+    srcs = ["generated_props.bzl"],
+    visibility = ["//visibility:public"],
+    deps = [
+        "@bazel_lib//lib:write_source_files",
+        "@xml.bzl//:xml",
+    ],
+)