build: Support dot/plantuml.jar paths via build environment variables

This also adds Java binary path override

Signed-off-by: Daniel Silverstone <dsilvers@digital-scurf.org>

2 files changed, 35 insertions, 3 deletions

diff --git a/build.rs b/build.rs
index 1852601..e86db58 100644
--- a/build.rs
+++ b/build.rs
@@ -118,6 +118,24 @@ fn write_out_resource_file<'a>(paths: impl Iterator<Item = &'a Path>) -> Result<
     Ok(())
 }
 
+/// Adopt an environment variable into the build.
+///
+/// This entails watching `SUBPLOT_{var}` and setting build environment
+/// to contain `BUILTIN_{var}` to either the env value, or `{def}` if not
+/// provided.
+fn adopt_env_var(var: &str, def: &str) {
+    println!("cargo:rerun-if-env-changed=SUBPLOT_{var}", var = var);
+    if let Ok(value) = std::env::var(format!("SUBPLOT_{var}", var = var)) {
+        println!(
+            "cargo:rustc-env=BUILTIN_{var}={value}",
+            var = var,
+            value = value
+        );
+    } else {
+        println!("cargo:rustc-env=BUILTIN_{var}={def}", var = var, def = def);
+    }
+}
+
 fn main() {
     println!("cargo:rerun-if-env-changed=DEB_BUILD_OPTIONS");
     let paths = if std::env::var("DEB_BUILD_OPTIONS").is_err() {
@@ -129,4 +147,7 @@ fn main() {
     };
     write_out_resource_file(paths.iter().map(PathBuf::as_path))
         .expect("Unable to write the resource file out");
+    adopt_env_var("DOT_PATH", "dot");
+    adopt_env_var("PLANTUML_JAR_PATH", "/usr/share/plantuml/plantuml.jar");
+    adopt_env_var("JAVA_PATH", "java");
 }
diff --git a/src/graphmarkup.rs b/src/graphmarkup.rs
index 78ffe89..f5637dc 100644
--- a/src/graphmarkup.rs
+++ b/src/graphmarkup.rs
@@ -29,6 +29,13 @@ pub struct MarkupOpts {
         env = "SUBPLOT_PLANTUML_JAR_PATH"
     )]
     plantuml_jar_path: Option<PathBuf>,
+    #[structopt(
+        long = "java",
+        help = "Path to Java executable (note, effectively overrides JAVA_HOME if set to an absolute path)",
+        name = "JAVA_PATH",
+        env = "SUBPLOT_JAVA_PATH"
+    )]
+    java_path: Option<PathBuf>,
 }
 
 impl MarkupOpts {
@@ -40,13 +47,17 @@ impl MarkupOpts {
         if let Some(plantuml_path) = &self.plantuml_jar_path {
             *PLANTUML_JAR_PATH.lock().unwrap() = plantuml_path.clone();
         }
+        if let Some(java_path) = &self.java_path {
+            *JAVA_PATH.lock().unwrap() = java_path.clone();
+        }
     }
 }
 
 lazy_static! {
-    static ref DOT_PATH: Mutex<PathBuf> = Mutex::new("dot".into());
+    static ref DOT_PATH: Mutex<PathBuf> = Mutex::new(env!("BUILTIN_DOT_PATH").into());
     static ref PLANTUML_JAR_PATH: Mutex<PathBuf> =
-        Mutex::new("/usr/share/plantuml/plantuml.jar".into());
+        Mutex::new(env!("BUILTIN_PLANTUML_JAR_PATH").into());
+    static ref JAVA_PATH: Mutex<PathBuf> = Mutex::new(env!("BUILTIN_JAVA_PATH").into());
 }
 
 /// A code block with markup for a graph.
@@ -181,7 +192,7 @@ impl PlantumlMarkup {
 
 impl GraphMarkup for PlantumlMarkup {
     fn as_svg(&self) -> Result<Vec<u8>> {
-        let mut cmd = Command::new("java");
+        let mut cmd = Command::new(JAVA_PATH.lock().unwrap().clone());
         cmd.arg("-Djava.awt.headless=true")
             .arg("-jar")
             .arg(PLANTUML_JAR_PATH.lock().unwrap().clone())