Postpone the initialization of the CAS client in hg until we know we need it

Summary:
Most hg commands don't need CAS, initializing it is wasteful and also leads to more noise on stderr, which in turn is bad for integration tests.

Simply postponing the initialization reduces the surface to a more manageable one.

Reviewed By: chiara125

Differential Revision: D75939889

fbshipit-source-id: 5112c6db3974c471a278820f4875db79817b856b

Author: andreacampi

eden/scm/BUCK

@@ -3,7 +3,7 @@
 # fix the mercurial code to use fbcode-relative includes.
 #
 
-load("@fbcode//eden/scm:targets.bzl", "fetch_as_eden", "gen_hgpython", "hg_binary")
+load("@fbcode//eden/scm:targets.bzl", "gen_hgpython", "hg_binary")
 load("@fbcode_macros//build_defs:cpp_binary.bzl", "cpp_binary")
 load("@fbcode_macros//build_defs:cpp_library.bzl", "cpp_library")
 load("@fbcode_macros//build_defs:export_files.bzl", "export_file")
@@ -182,10 +182,6 @@ hg_binary(
         "DEFAULT": None,
         "ovr_config//build_mode/constraints:dev": PYTHON_EXTREME_LINK_GROUP_THRESHOLD,
     }),
-    named_deps = select({
-        "DEFAULT": {},
-        "ovr_config//os:linux": {} if rust_oss.is_oss_build() else ({"cas_client": "//eden/scm/lib/cas-client/rich-client:rich-cas-client"} if fetch_as_eden() else {"cas_client": "//eden/scm/lib/cas-client/thin-client:thin-cas-client"}),
-    }),
 )
 
 hg_binary(

eden/scm/exec/hgmain/src/main.rs

@@ -110,9 +110,6 @@ fn main() {
     #[cfg(windows)]
     windows::enable_vt_processing().unwrap();
 
-    #[cfg(feature = "cas")]
-    cas_client::init();
-
     let mut io = clidispatch::io::IO::stdio();
 
     let _ = io.setup_term();
@@ -176,12 +173,7 @@ pub fn drop_root(user: &str, group: &str) {
     let home_dir = unsafe { (*libc_user).pw_dir };
     if !home_dir.is_null() {
         // TODO: Audit that the environment access only happens in single-threaded code.
-        unsafe {
-            std::env::set_var(
-                "HOME",
-                unsafe { CStr::from_ptr(home_dir) }.to_str().unwrap(),
-            )
-        };
+        unsafe { std::env::set_var("HOME", CStr::from_ptr(home_dir).to_str().unwrap()) };
     }
     // TODO: Audit that the environment access only happens in single-threaded code.
     unsafe { std::env::set_var("USER", user) };

eden/scm/lib/clidispatch/BUCK

@@ -1,4 +1,6 @@
+load("@fbcode//eden/scm:targets.bzl", "fetch_as_eden")
 load("@fbcode_macros//build_defs:rust_library.bzl", "rust_library")
+load("@fbcode_macros//build_defs/lib:rust_oss.bzl", "rust_oss")
 
 oncall("sapling")
 
@@ -29,7 +31,14 @@ rust_library(
     }},
     features = [
         "eden",
-    ],
+    ] + select({
+        "DEFAULT": [],
+        "ovr_config//os:linux": [] if rust_oss.is_oss_build() else ["cas"],
+    }),
+    named_deps = select({
+        "DEFAULT": {},
+        "ovr_config//os:linux": {} if rust_oss.is_oss_build() else ({"cas_client": "//eden/scm/lib/cas-client/rich-client:rich-cas-client"} if fetch_as_eden() else {"cas_client": "//eden/scm/lib/cas-client/thin-client:thin-cas-client"}),
+    }),
     deps = [
         "fbsource//third-party/rust:anyhow",
         "fbsource//third-party/rust:erased-serde",

eden/scm/lib/clidispatch/src/command.rs

@@ -34,6 +34,7 @@ pub struct CommandDefinition {
     flags_func: fn() -> Vec<Flag>,
     func: CommandFunc,
     synopsis: Option<String>,
+    enable_cas: bool,
 }
 
 impl CommandDefinition {
@@ -43,13 +44,15 @@ impl CommandDefinition {
         flags_func: fn() -> Vec<Flag>,
         func: CommandFunc,
         synopsis: Option<impl ToString>,
+        enable_cas: bool,
     ) -> Self {
         CommandDefinition {
             aliases: aliases.to_string(),
             doc: doc.to_string(),
             flags_func,
             func,
             synopsis: synopsis.map(|s| s.to_string()),
+            enable_cas,
         }
     }
 
@@ -78,6 +81,10 @@ impl CommandDefinition {
             .split('|')
             .find_map(|a| a.strip_prefix("legacy:"))
     }
+
+    pub fn enable_cas(&self) -> bool {
+        self.enable_cas
+    }
 }
 
 #[derive(Default)]
@@ -129,7 +136,14 @@ impl Deref for CommandTable {
 }
 
 pub trait Register<FN, T> {
-    fn register(&mut self, f: FN, aliases: &str, doc: &str, synopsis: Option<&str>);
+    fn register(
+        &mut self,
+        f: FN,
+        aliases: &str,
+        doc: &str,
+        synopsis: Option<&str>,
+        enable_cas: bool,
+    );
 }
 
 // OptionalRepo commands.
@@ -138,7 +152,14 @@ where
     S: TryFrom<ParseOutput, Error = anyhow::Error> + StructFlags,
     FN: Fn(ReqCtx<S>, Option<&Repo>) -> Result<u8> + 'static,
 {
-    fn register(&mut self, f: FN, aliases: &str, doc: &str, synopsis: Option<&str>) {
+    fn register(
+        &mut self,
+        f: FN,
+        aliases: &str,
+        doc: &str,
+        synopsis: Option<&str>,
+        enable_cas: bool,
+    ) {
         self.insert_aliases(aliases);
         let func = move |opts: ParseOutput, io: &IO, repo: &OptionalRepo| {
             f(
@@ -147,7 +168,7 @@ where
             )
         };
         let func = CommandFunc::OptionalRepo(Box::new(func));
-        let def = CommandDefinition::new(aliases, doc, S::flags, func, synopsis);
+        let def = CommandDefinition::new(aliases, doc, S::flags, func, synopsis, enable_cas);
         self.commands.insert(aliases.to_string(), def);
     }
 }
@@ -158,13 +179,20 @@ where
     S: TryFrom<ParseOutput, Error = anyhow::Error> + StructFlags,
     FN: Fn(ReqCtx<S>, &Repo) -> Result<u8> + 'static,
 {
-    fn register(&mut self, f: FN, aliases: &str, doc: &str, synopsis: Option<&str>) {
+    fn register(
+        &mut self,
+        f: FN,
+        aliases: &str,
+        doc: &str,
+        synopsis: Option<&str>,
+        enable_cas: bool,
+    ) {
         self.insert_aliases(aliases);
         let func = move |opts: ParseOutput, io: &IO, repo: &Repo| {
             f(ReqCtx::new(repo.config().clone(), opts, io.clone())?, repo)
         };
         let func = CommandFunc::Repo(Box::new(func));
-        let def = CommandDefinition::new(aliases, doc, S::flags, func, synopsis);
+        let def = CommandDefinition::new(aliases, doc, S::flags, func, synopsis, enable_cas);
         self.commands.insert(aliases.to_string(), def);
     }
 }
@@ -175,13 +203,20 @@ where
     S: TryFrom<ParseOutput, Error = anyhow::Error> + StructFlags,
     FN: Fn(ReqCtx<S>) -> Result<u8> + 'static,
 {
-    fn register(&mut self, f: FN, aliases: &str, doc: &str, synopsis: Option<&str>) {
+    fn register(
+        &mut self,
+        f: FN,
+        aliases: &str,
+        doc: &str,
+        synopsis: Option<&str>,
+        enable_cas: bool,
+    ) {
         self.insert_aliases(aliases);
         let func = move |opts: ParseOutput, io: &IO, config: &Arc<dyn Config>| {
             f(ReqCtx::new(config.clone(), opts, io.clone())?)
         };
         let func = CommandFunc::NoRepo(Box::new(func));
-        let def = CommandDefinition::new(aliases, doc, S::flags, func, synopsis);
+        let def = CommandDefinition::new(aliases, doc, S::flags, func, synopsis, enable_cas);
         self.commands.insert(aliases.to_string(), def);
     }
 }
@@ -192,7 +227,14 @@ where
     S: TryFrom<ParseOutput, Error = anyhow::Error> + StructFlags,
     FN: Fn(ReqCtx<S>, &Repo, &WorkingCopy) -> Result<u8> + 'static,
 {
-    fn register(&mut self, f: FN, aliases: &str, doc: &str, synopsis: Option<&str>) {
+    fn register(
+        &mut self,
+        f: FN,
+        aliases: &str,
+        doc: &str,
+        synopsis: Option<&str>,
+        enable_cas: bool,
+    ) {
         self.insert_aliases(aliases);
         let func = move |opts: ParseOutput, io: &IO, repo: &Repo, working_copy: &WorkingCopy| {
             f(
@@ -202,7 +244,7 @@ where
             )
         };
         let func = CommandFunc::WorkingCopy(Box::new(func));
-        let def = CommandDefinition::new(aliases, doc, S::flags, func, synopsis);
+        let def = CommandDefinition::new(aliases, doc, S::flags, func, synopsis, enable_cas);
         self.commands.insert(aliases.to_string(), def);
     }
 }

eden/scm/lib/clidispatch/src/dispatch.rs

@@ -450,6 +450,11 @@ impl Dispatcher {
                 self.convert_to_repoless_config()?;
             }
 
+            #[cfg(feature = "cas")]
+            if handler.enable_cas() {
+                cas_client::init();
+            }
+
             hooks.run_pre(self.repo(), &self.args[1..])?;
 
             let res = match handler.func() {

eden/scm/lib/commands/BUCK

@@ -1,4 +1,6 @@
+load("@fbcode//eden/scm:targets.bzl", "fetch_as_eden")
 load("@fbcode_macros//build_defs:rust_library.bzl", "rust_library")
+load("@fbcode_macros//build_defs/lib:rust_oss.bzl", "rust_oss")
 
 oncall("sapling")
 
@@ -51,7 +53,14 @@ rust_library(
     features = [
         "eden",
         "fb",
-    ],
+    ] + select({
+        "DEFAULT": [],
+        "ovr_config//os:linux": [] if rust_oss.is_oss_build() else ["cas"],
+    }),
+    named_deps = select({
+        "DEFAULT": {},
+        "ovr_config//os:linux": {} if rust_oss.is_oss_build() else ({"cas_client": "//eden/scm/lib/cas-client/rich-client:rich-cas-client"} if fetch_as_eden() else {"cas_client": "//eden/scm/lib/cas-client/thin-client:thin-cas-client"}),
+    }),
     deps = [
         "fbsource//third-party/rust:anyhow",
         "fbsource//third-party/rust:ctrlc",

eden/scm/lib/commands/commands/cmdclone/src/lib.rs

@@ -789,3 +789,7 @@ pub fn doc() -> &'static str {
 pub fn synopsis() -> Option<&'static str> {
     Some("[OPTION]... SOURCE [DEST]")
 }
+
+pub fn enable_cas() -> bool {
+    true
+}

eden/scm/lib/commands/commands/cmdconfig/src/lib.rs

@@ -339,3 +339,7 @@ pub fn synopsis() -> Option<&'static str> {
 fn short_name() -> &'static str {
     "config"
 }
+
+pub fn enable_cas() -> bool {
+    false
+}

eden/scm/lib/commands/commands/cmdconfigfile/src/lib.rs

@@ -87,3 +87,7 @@ pub fn doc() -> &'static str {
 pub fn synopsis() -> Option<&'static str> {
     None
 }
+
+pub fn enable_cas() -> bool {
+    false
+}

eden/scm/lib/commands/commands/cmdgoto/src/lib.rs

@@ -294,3 +294,7 @@ Returns 0 on success, 1 if there are unresolved files."#
 pub fn synopsis() -> Option<&'static str> {
     Some("[OPTION]... [REV]")
 }
+
+pub fn enable_cas() -> bool {
+    true
+}