From 7ebea035f3d7f616d42f520f822120133edec539 Mon Sep 17 00:00:00 2001
From: ascopes <73482956+ascopes@users.noreply.github.com>
Date: Sun, 21 Jan 2024 09:56:15 +0000
Subject: [PATCH] Allow overriding protoc.version via the commandline with
 higher precedence than <protocVersion>

---
 .../protobufmavenplugin/AbstractGenerateMojo.java    | 12 +++++++++++-
 src/site/markdown/index.md                           |  7 +++++++
 2 files changed, 18 insertions(+), 1 deletion(-)

diff --git a/src/main/java/io/github/ascopes/protobufmavenplugin/AbstractGenerateMojo.java b/src/main/java/io/github/ascopes/protobufmavenplugin/AbstractGenerateMojo.java
index fa034ca3..b049c98f 100644
--- a/src/main/java/io/github/ascopes/protobufmavenplugin/AbstractGenerateMojo.java
+++ b/src/main/java/io/github/ascopes/protobufmavenplugin/AbstractGenerateMojo.java
@@ -250,7 +250,7 @@ public void execute() throws MojoExecutionException, MojoFailureException {
         .isLiteEnabled(liteOnly)
         .mavenSession(session)
         .outputDirectory(actualOutputDirectory)
-        .protocVersion(protocVersion)
+        .protocVersion(protocVersion())
         .sourceRootRegistrar(sourceRootRegistrar())
         .build();
 
@@ -338,6 +338,16 @@ protected void validate() {
         });
   }
 
+  private String protocVersion() {
+    // Give precedence to overriding the protoc version via the command line
+    // in case the Maven binaries are incompatible with the current system.
+    var overriddenVersion = System.getProperty("protoc.version");
+    if (overriddenVersion != null) {
+      return overriddenVersion;
+    }
+    return protocVersion;
+  }
+
   private Collection<Path> parsePaths(@Nullable Collection<String> paths) {
     if (paths == null) {
       return List.of();
diff --git a/src/site/markdown/index.md b/src/site/markdown/index.md
index c5a809d2..e1424ba2 100644
--- a/src/site/markdown/index.md
+++ b/src/site/markdown/index.md
@@ -57,6 +57,13 @@ and will be output to `target/generated-sources/protobuf`
 (or `target/generated-test-sources/protobuf` for tests). This can be overridden
 in the `configuration` block if needed.
 
+The `protoc` version itself can be set via the `<protocVersion>` configuration parameter
+as shown above, or can be set via the `protoc.version` property in your POM. It may
+optionally be totally overridden on the command line by passing `-Dprotoc.version=xxx`,
+in which case the `<protocVersion>` and `protoc.version` will be ignored. This is done
+to allow users who may have an incompatible system to be able to request a build using
+the `$PATH`-based `protoc` binary on their system (documented later in this page).
+
 ## Dependencies
 
 It is worth noting that you will need to include the `protobuf-java` dependency