fix: windows support for path loading

.github/workflows/ci.yaml

@@ -12,9 +12,11 @@ jobs:
 
     steps:
     - uses: actions/checkout@v2
-    - uses: golangci/golangci-lint-action@v2
+    - uses: golangci/golangci-lint-action@v3
       with:
         args: --timeout=5m
+        version: latest
+        only-new-issues: true
 
   build:
     runs-on: ${{ matrix.os }}
@@ -24,7 +26,7 @@ jobs:
     strategy:
       matrix:
         # No Windows this time. Some tests expect Unix-style paths.
-        os: [ ubuntu-latest, macos-latest ]
+        os: [ ubuntu-latest, macos-latest, windows-latest]
       fail-fast: false
 
     steps:

.golangci.yml

@@ -11,7 +11,7 @@ linters-settings:
     threshold: 100
   goconst:
     min-len: 3
-    min-occurrences: 2
+    min-occurrences: 3
 
 linters:
   enable-all: true
@@ -52,3 +52,7 @@ linters:
     - nilnil
     - nonamedreturns
     - nosnakecase
+    - depguard
+    # temporarily disabled
+    - goconst
+    - testifylint

loading.go

@@ -21,6 +21,7 @@
 	"net/http"
 	"net/url"
 	"os"
+	"path"
 	"path/filepath"
 	"runtime"
 	"strings"
@@ -40,43 +41,97 @@
 var LoadHTTPCustomHeaders = map[string]string{}
 
 // LoadFromFileOrHTTP loads the bytes from a file or a remote http server based on the path passed in
-func LoadFromFileOrHTTP(path string) ([]byte, error) {
-	return LoadStrategy(path, os.ReadFile, loadHTTPBytes(LoadHTTPTimeout))(path)
+func LoadFromFileOrHTTP(pth string) ([]byte, error) {
+	return LoadStrategy(pth, os.ReadFile, loadHTTPBytes(LoadHTTPTimeout))(pth)
 }
 
 // LoadFromFileOrHTTPWithTimeout loads the bytes from a file or a remote http server based on the path passed in
 // timeout arg allows for per request overriding of the request timeout
-func LoadFromFileOrHTTPWithTimeout(path string, timeout time.Duration) ([]byte, error) {
-	return LoadStrategy(path, os.ReadFile, loadHTTPBytes(timeout))(path)
+func LoadFromFileOrHTTPWithTimeout(pth string, timeout time.Duration) ([]byte, error) {
+	return LoadStrategy(pth, os.ReadFile, loadHTTPBytes(timeout))(pth)
 }
 
-// LoadStrategy returns a loader function for a given path or uri
-func LoadStrategy(path string, local, remote func(string) ([]byte, error)) func(string) ([]byte, error) {
-	if strings.HasPrefix(path, "http") {
+// LoadStrategy returns a loader function for a given path or URI.
+//
+// The load strategy returns the remote load for any path starting with `http`.
+// So this works for any URI with a scheme `http` or `https`.
+//
+// The fallback strategy is to call the local loader.
+//
+// The local loader takes a local file system path (absolute or relative) as argument,
+// or alternatively a `file://...` URI, **without host** (see also below for windows).
+//
+// There are a few liberalities, initially intended to be tolerant regarding the URI syntax,
+// especially on windows.
+//
+// Before the local loader is called, the given path is transformed:
+//   - percent-encoded characters are unescaped
+//   - simple paths (e.g. `./folder/file`) are passed as-is
+//   - on windows, occurrences of `/` are replaced by `\`, so providing a relative path such a `folder/file` works too.
+//
+// For paths provided as URIs with the "file" scheme, please note that:
+//   - `file://` is simply stripped.
+//     This means that the host part of the URI is not parsed at all.
+//     For example, `file:///folder/file" becomes "/folder/file`,
+//     but `file://localhost/folder/file` becomes `localhost/folder/file` on unix systems.
+//     Similarly, `file://./folder/file` yields `./folder/file`.
+//   - on windows, `file://...` can take a host so as to specify an UNC share location.
+//
+// Reminder about windows-specifics:
+// - `file://host/folder/file` becomes an UNC path like `\\host\folder\file` (no port specification is supported)
+// - `file:///c:/folder/file` becomes `C:\folder\file`
+// - `file://c:/folder/file` is tolerated (without leading `/`) and becomes `c:\folder\file`
+func LoadStrategy(pth string, local, remote func(string) ([]byte, error)) func(string) ([]byte, error) {
+	if strings.HasPrefix(pth, "http") {
 		return remote
 	}
-	return func(pth string) ([]byte, error) {
-		upth, err := pathUnescape(pth)
+
+	return func(p string) ([]byte, error) {
+		upth, err := pathUnescape(p)
 		if err != nil {
 			return nil, err
 		}
 
-		if strings.HasPrefix(pth, `file://`) {
-			if runtime.GOOS == "windows" {
-				// support for canonical file URIs on windows.
-				// Zero tolerance here for dodgy URIs.
-				u, _ := url.Parse(upth)
-				if u.Host != "" {
-					// assume UNC name (volume share)
-					// file://host/share/folder\... ==> \\host\share\path\folder
-					// NOTE: UNC port not yet supported
-					upth = strings.Join([]string{`\`, u.Host, u.Path}, `\`)
-				} else {
-					// file:///c:/folder/... ==> just remove the leading slash
-					upth = strings.TrimPrefix(upth, `file:///`)
-				}
-			} else {
-				upth = strings.TrimPrefix(upth, `file://`)
+		if !strings.HasPrefix(p, `file://`) {
+			// regular file path provided: just normalize slashes
+			return local(filepath.FromSlash(upth))
+		}
+
+		if runtime.GOOS != "windows" {
+			// crude processing: this leaves full URIs with a host with a (mostly) unexpected result
+			upth = strings.TrimPrefix(upth, `file://`)
+
+			return local(filepath.FromSlash(upth))
+		}
+
+		// windows-only pre-processing of file://... URIs
+
+		// support for canonical file URIs on windows.
+		u, err := url.Parse(filepath.ToSlash(upth))
+		if err != nil {
+			return nil, err
+		}
+
+		if u.Host != "" {
+			// assume UNC name (volume share)
+			// NOTE: UNC port not yet supported
+
+			// when the "host" segment is a drive letter:
+			// file://C:/folder/... => C:\folder
+			upth = path.Clean(strings.Join([]string{u.Host, u.Path}, `/`))
+			if !strings.HasSuffix(u.Host, ":") && u.Host[0] != '.' {
+				// tolerance: if we have a leading dot, this can't be a host
+				// file://host/share/folder\... ==> \\host\share\path\folder
+				upth = "//" + upth
+			}
+		} else {
+			// no host, let's figure out if this is a drive letter
+			upth = strings.TrimPrefix(upth, `file://`)
+			first, _, _ := strings.Cut(strings.TrimPrefix(u.Path, "/"), "/")
+			if strings.HasSuffix(first, ":") {
+				// drive letter in the first segment:
+				// file:///c:/folder/... ==> strip the leading slash
+				upth = strings.TrimPrefix(upth, `/`)
 			}
 		}