move browser opening logic in Builder

This allows open() to be called from other places in bootstrap (I need
this for Ferrocene), and it simplifies the callers by moving the
"was_invoked_explicitly" check into the function.

Author: pietroalbini

Diff for: src/bootstrap/builder.rs

@@ -2207,6 +2207,24 @@ impl<'a> Builder<'a> {
 
         false
     }
+
+    pub(crate) fn maybe_open_in_browser<S: Step>(&self, path: impl AsRef<Path>) {
+        if self.was_invoked_explicitly::<S>(Kind::Doc) {
+            self.open_in_browser(path);
+        }
+    }
+
+    pub(crate) fn open_in_browser(&self, path: impl AsRef<Path>) {
+        if self.config.dry_run || !self.config.cmd.open() {
+            return;
+        }
+
+        let path = path.as_ref();
+        self.info(&format!("Opening doc {}", path.display()));
+        if let Err(err) = opener::open(path) {
+            self.info(&format!("{}\n", err));
+        }
+    }
 }
 
 #[cfg(test)]

Diff for: src/bootstrap/doc.rs

@@ -12,7 +12,7 @@ use std::fs;
 use std::io;
 use std::path::{Path, PathBuf};
 
-use crate::builder::{Builder, Compiler, Kind, RunConfig, ShouldRun, Step};
+use crate::builder::{Builder, Compiler, RunConfig, ShouldRun, Step};
 use crate::cache::{Interned, INTERNER};
 use crate::compile;
 use crate::config::{Config, TargetSelection};
@@ -85,18 +85,6 @@ book!(
     StyleGuide, "src/doc/style-guide", "style-guide";
 );
 
-fn open(builder: &Builder<'_>, path: impl AsRef<Path>) {
-    if builder.config.dry_run || !builder.config.cmd.open() {
-        return;
-    }
-
-    let path = path.as_ref();
-    builder.info(&format!("Opening doc {}", path.display()));
-    if let Err(err) = opener::open(path) {
-        builder.info(&format!("{}\n", err));
-    }
-}
-
 // "library/std" -> ["library", "std"]
 //
 // Used for deciding whether a particular step is one requested by the user on
@@ -240,11 +228,9 @@ impl Step for TheBook {
             invoke_rustdoc(builder, compiler, &shared_assets, target, path);
         }
 
-        if builder.was_invoked_explicitly::<Self>(Kind::Doc) {
-            let out = builder.doc_out(target);
-            let index = out.join("book").join("index.html");
-            open(builder, &index);
-        }
+        let out = builder.doc_out(target);
+        let index = out.join("book").join("index.html");
+        builder.maybe_open_in_browser::<Self>(index);
     }
 }
 
@@ -384,10 +370,7 @@ impl Step for Standalone {
 
         // We open doc/index.html as the default if invoked as `x.py doc --open`
         // with no particular explicit doc requested (e.g. library/core).
-        if builder.paths.is_empty() || builder.was_invoked_explicitly::<Self>(Kind::Doc) {
-            let index = out.join("index.html");
-            open(builder, &index);
-        }
+        builder.maybe_open_in_browser::<Self>(out.join("index.html"));
     }
 }
 
@@ -507,7 +490,7 @@ impl Step for Std {
         for requested_crate in requested_crates {
             if STD_PUBLIC_CRATES.iter().any(|k| *k == requested_crate.as_str()) {
                 let index = out.join(requested_crate).join("index.html");
-                open(builder, &index);
+                builder.open_in_browser(index);
             }
         }
     }
@@ -759,7 +742,7 @@ impl Step for Rustc {
         // Let's open the first crate documentation page:
         if let Some(krate) = to_open {
             let index = out.join(krate).join("index.html");
-            open(builder, &index);
+            builder.open_in_browser(index);
         }
     }
 }
@@ -1019,10 +1002,9 @@ impl Step for RustcBook {
             name: INTERNER.intern_str("rustc"),
             src: INTERNER.intern_path(out_base),
         });
-        if builder.was_invoked_explicitly::<Self>(Kind::Doc) {
-            let out = builder.doc_out(self.target);
-            let index = out.join("rustc").join("index.html");
-            open(builder, &index);
-        }
+
+        let out = builder.doc_out(self.target);
+        let index = out.join("rustc").join("index.html");
+        builder.maybe_open_in_browser::<Self>(index);
     }
 }