Less automatic build.rs shenanigans

crates/re_build_info/src/build_info.rs

@@ -42,6 +42,8 @@ pub struct BuildInfo {
     /// ISO 8601 / RFC 3339 build time.
     ///
     /// Example: `"2023-02-23T19:33:26Z"`
+    ///
+    /// Empty if unknown.
     pub datetime: &'static str,
 }
 
@@ -83,7 +85,9 @@ impl std::fmt::Display for BuildInfo {
             write!(f, "]")?;
         }
 
-        write!(f, " {target_triple}")?;
+        if !target_triple.is_empty() {
+            write!(f, " {target_triple}")?;
+        }
 
         if !git_branch.is_empty() {
             write!(f, " {git_branch}")?;
@@ -93,7 +97,9 @@ impl std::fmt::Display for BuildInfo {
             write!(f, " {git_hash}")?;
         }
 
-        write!(f, ", built {datetime}")?;
+        if !datetime.is_empty() {
+            write!(f, ", built {datetime}")?;
+        }
 
         Ok(())
     }

crates/re_build_tools/src/git.rs

@@ -0,0 +1,65 @@
+//! # Situations to consider regarding git
+//!
+//! ## Using the published crate
+//!
+//! The published crate carries its version around, which in turns gives us the git tag, which makes
+//! the commit hash irrelevant.
+//! We still need to compute _something_ so that we can actually build, but that value will be
+//! ignored when the crate is built by the end user anyhow.
+//!
+//! ## Working directly within the workspace
+//!
+//! When working within the workspace, we can simply try and call `git` and we're done.
+//!
+//! ## Using an unpublished crate (e.g. `path = "…"` or `git = "…"` or `[patch.crates-io]`)
+//!
+//! In these cases we may or may not have access to the workspace (e.g. a `path = …` import likely
+//! will, while a crate patch won't).
+//!
+//! This is not an issue however, as we can simply try and see what we get.
+//! If we manage to compute a commit hash, great, otherwise we still have the crate version to
+//! fallback on.
+
+use std::path::PathBuf;
+
+use crate::{rerun_if_changed, run_command};
+
+pub fn rebuild_if_branch_or_commit_changes() {
+    if let Ok(head_path) = git_path("HEAD") {
+        rerun_if_changed(&head_path); // Track changes to branch
+        if let Ok(head) = std::fs::read_to_string(&head_path) {
+            if let Some(git_file) = head.strip_prefix("ref: ") {
+                if let Ok(path) = git_path(git_file) {
+                    if path.exists() {
+                        rerun_if_changed(path); // Track changes to commit hash
+                    } else {
+                        // Weird that it doesn't exist. Maybe we will miss a git hash change,
+                        // but that is better that tracking a non-existing files (which leads to constant rebuilds).
+                        // See https://github.com/rerun-io/rerun/issues/2380 for more
+                    }
+                }
+            }
+        }
+    }
+}
+
+pub fn commit_hash() -> anyhow::Result<String> {
+    let git_hash = run_command("git", &["rev-parse", "HEAD"])?;
+    if git_hash.is_empty() {
+        anyhow::bail!("empty commit hash");
+    }
+    Ok(git_hash)
+}
+
+pub fn branch() -> anyhow::Result<String> {
+    run_command("git", &["symbolic-ref", "--short", "HEAD"])
+}
+
+/// From <https://git-scm.com/docs/git-rev-parse>:
+///
+/// Resolve `$GIT_DIR/<path>` and takes other path relocation variables such as `$GIT_OBJECT_DIRECTORY`, `$GIT_INDEX_FILE…​` into account.
+/// For example, if `$GIT_OBJECT_DIRECTORY` is set to /foo/bar then `git rev-parse --git-path objects/abc` returns `/foo/bar/abc`.
+fn git_path(path: &str) -> anyhow::Result<PathBuf> {
+    let path = run_command("git", &["rev-parse", "--git-path", path])?;
+    Ok(path.into())
+}

crates/re_build_tools/src/lib.rs

@@ -1,12 +1,14 @@
 #![allow(clippy::unwrap_used)]
+#![warn(missing_docs)]
 
 //! This crate is to be used from `build.rs` build scripts.
 
 use anyhow::Context as _;
 
+use std::process::Command;
 use std::sync::atomic::{AtomicBool, Ordering};
-use std::{path::PathBuf, process::Command};
 
+mod git;
 mod hashing;
 mod rebuild_detector;
 
@@ -21,6 +23,24 @@ pub use self::rebuild_detector::{
     rerun_if_changed_glob, rerun_if_changed_or_doesnt_exist, write_file_if_necessary,
 };
 
+// ------------------
+
+/// Should we export the build datetime for developers in the workspace?
+///
+/// It will be visible in analytics, in the viewer's about-menu, and with `rerun --version`.
+///
+/// To do so accurately may incur unnecessary recompiles, so only turn this on if you really need it.
+const EXPORT_BUILD_TIME_FOR_DEVELOPERS: bool = false;
+
+/// Should we export the current git hash/branch for developers in the workspace?
+///
+/// It will be visible in analytics, in the viewer's about-menu, and with `rerun --version`.
+///
+/// To do so accurately may incur unnecessary recompiles, so only turn this on if you really need it.
+const EXPORT_GIT_FOR_DEVELOPERS: bool = false;
+
+// ------------------
+
 /// Atomic bool indicating whether or not to print the cargo build instructions
 pub(crate) static OUTPUT_CARGO_BUILD_INSTRUCTIONS: AtomicBool = AtomicBool::new(true);
 
@@ -34,6 +54,8 @@ pub(crate) fn should_output_cargo_build_instructions() -> bool {
     OUTPUT_CARGO_BUILD_INSTRUCTIONS.load(Ordering::Relaxed)
 }
 
+// ------------------
+
 /// Where is this `build.rs` build script running?
 pub enum Environment {
     /// We are running `cargo publish` (via `scripts/ci/crates.py`); _probably_ on CI.
@@ -87,79 +109,84 @@ pub fn is_on_ci() -> bool {
 ///
 /// Use this crate together with the `re_build_info` crate.
 pub fn export_build_info_vars_for_crate(crate_name: &str) {
-    rebuild_if_crate_changed(crate_name);
-    export_build_info_env_vars();
-}
+    let environment = Environment::detect();
 
-/// # Situations to consider regarding git
-///
-/// ## Using the published crate
-///
-/// The published crate carries its version around, which in turns gives us the git tag, which makes
-/// the commit hash irrelevant.
-/// We still need to compute _something_ so that we can actually build, but that value will be
-/// ignored when the crate is built by the end user anyhow.
-///
-/// ## Working directly within the workspace
-///
-/// When working within the workspace, we can simply try and call `git` and we're done.
-///
-/// ## Using an unpublished crate (e.g. `path = "…"` or `git = "…"` or `[patch.crates-io]`)
-///
-/// In these cases we may or may not have access to the workspace (e.g. a `path = …` import likely
-/// will, while a crate patch won't).
-///
-/// This is not an issue however, as we can simply try and see what we get.
-/// If we manage to compute a commit hash, great, otherwise we still have the crate version to
-/// fallback on.
-fn export_build_info_env_vars() {
-    // target triple
-    set_env("RE_BUILD_TARGET_TRIPLE", &std::env::var("TARGET").unwrap());
-    set_env("RE_BUILD_GIT_HASH", &git_hash().unwrap_or_default());
-    set_env("RE_BUILD_GIT_BRANCH", &git_branch().unwrap_or_default());
-
-    // rust version
-    let (rustc, llvm) = rust_version().unwrap_or_default();
-    set_env("RE_BUILD_RUSTC_VERSION", &rustc);
-    set_env("RE_BUILD_LLVM_VERSION", &llvm);
-
-    // We need to check `IS_IN_RERUN_WORKSPACE` in the build-script (here),
-    // because otherwise it won't show up when compiling through maturin.
-    // We must also make an exception for when we build actual wheels (on CI) for release.
-    if is_on_ci() {
-        // e.g. building wheels on CI.
-        set_env("RE_BUILD_IS_IN_RERUN_WORKSPACE", "no");
+    let export_datetime = match environment {
+        Environment::PublishingCrates | Environment::CI => true,
+
+        Environment::DeveloperInWorkspace => EXPORT_BUILD_TIME_FOR_DEVELOPERS,
+
+        // Datetime won't always be accurate unless we rebuild as soon as a dependency changes,
+        // and we don't want to add that burden to our users.
+        Environment::UsedAsDependency => false,
+    };
+
+    let export_git_info = match environment {
+        Environment::PublishingCrates | Environment::CI => true,
+
+        Environment::DeveloperInWorkspace => EXPORT_GIT_FOR_DEVELOPERS,
+
+        // We shouldn't show the users git hash/branch in the rerun viewer.
+        Environment::UsedAsDependency => false,
+    };
+
+    if export_datetime {
+        set_env("RE_BUILD_DATETIME", &date_time());
+
+        // The only way to make sure the build datetime is up-to-date is to run
+        // `build.rs` on every build, and there is really no good way of doing
+        // so except to manually check if any files have changed:
+        rebuild_if_crate_changed(crate_name);
+    } else {
+        set_env("RE_BUILD_DATETIME", "");
+    }
+
+    if export_git_info {
+        set_env("RE_BUILD_GIT_HASH", &git::commit_hash().unwrap_or_default());
+        set_env("RE_BUILD_GIT_BRANCH", &git::branch().unwrap_or_default());
+
+        // Make sure the above are up-to-date
+        git::rebuild_if_branch_or_commit_changes();
     } else {
-        set_env(
-            "RE_BUILD_IS_IN_RERUN_WORKSPACE",
-            &std::env::var("IS_IN_RERUN_WORKSPACE").unwrap_or_default(),
-        );
+        set_env("RE_BUILD_GIT_HASH", "");
+        set_env("RE_BUILD_GIT_BRANCH", "");
     }
 
+    // Stuff that doesn't change, so doesn't need rebuilding:
+    {
+        // target triple
+        set_env("RE_BUILD_TARGET_TRIPLE", &std::env::var("TARGET").unwrap());
+
+        // rust version
+        let (rustc, llvm) = rust_llvm_versions().unwrap_or_default();
+        set_env("RE_BUILD_RUSTC_VERSION", &rustc);
+        set_env("RE_BUILD_LLVM_VERSION", &llvm);
+
+        // We need to check `IS_IN_RERUN_WORKSPACE` in the build-script (here),
+        // because otherwise it won't show up when compiling through maturin.
+        // We must also make an exception for when we build actual wheels (on CI) for release.
+        if is_on_ci() {
+            // e.g. building wheels on CI.
+            set_env("RE_BUILD_IS_IN_RERUN_WORKSPACE", "no");
+        } else {
+            set_env(
+                "RE_BUILD_IS_IN_RERUN_WORKSPACE",
+                &std::env::var("IS_IN_RERUN_WORKSPACE").unwrap_or_default(),
+            );
+        }
+    }
+}
+
+/// ISO 8601 / RFC 3339 build time.
+///
+/// Example: `"2023-02-23T19:33:26Z"`
+fn date_time() -> String {
     let time_format =
         time::format_description::parse("[year]-[month]-[day]T[hour]:[minute]:[second]Z").unwrap();
-    let date_time = time::OffsetDateTime::now_utc()
+
+    time::OffsetDateTime::now_utc()
         .format(&time_format)
-        .unwrap();
-    set_env("RE_BUILD_DATETIME", &date_time);
-
-    // Make sure we re-run the build script if the branch or commit changes:
-    if let Ok(head_path) = git_path("HEAD") {
-        rerun_if_changed(&head_path); // Track changes to branch
-        if let Ok(head) = std::fs::read_to_string(&head_path) {
-            if let Some(git_file) = head.strip_prefix("ref: ") {
-                if let Ok(path) = git_path(git_file) {
-                    if path.exists() {
-                        rerun_if_changed(path); // Track changes to commit hash
-                    } else {
-                        // Weird that it doesn't exist. Maybe we will miss a git hash change,
-                        // but that is better that tracking a non-existing files (which leads to constant rebuilds).
-                        // See https://github.com/rerun-io/rerun/issues/2380 for more
-                    }
-                }
-            }
-        }
-    }
+        .unwrap()
 }
 
 fn set_env(name: &str, value: &str) {
@@ -184,32 +211,11 @@ fn run_command(cmd: &str, args: &[&str]) -> anyhow::Result<String> {
     Ok(String::from_utf8(output.stdout)?.trim().to_owned())
 }
 
-fn git_hash() -> anyhow::Result<String> {
-    let git_hash = run_command("git", &["rev-parse", "HEAD"])?;
-    if git_hash.is_empty() {
-        anyhow::bail!("empty commit hash");
-    }
-    Ok(git_hash)
-}
-
-fn git_branch() -> anyhow::Result<String> {
-    run_command("git", &["symbolic-ref", "--short", "HEAD"])
-}
-
-/// From <https://git-scm.com/docs/git-rev-parse>:
-///
-/// Resolve `$GIT_DIR/<path>` and takes other path relocation variables such as `$GIT_OBJECT_DIRECTORY`, `$GIT_INDEX_FILE…​` into account.
-/// For example, if `$GIT_OBJECT_DIRECTORY` is set to /foo/bar then `git rev-parse --git-path objects/abc` returns `/foo/bar/abc`.
-fn git_path(path: &str) -> anyhow::Result<PathBuf> {
-    let path = run_command("git", &["rev-parse", "--git-path", path])?;
-    Ok(path.into())
-}
-
 /// Returns `(rustc, LLVM)` versions.
 ///
 /// Defaults to `"unknown"` if, for whatever reason, the output from `rustc -vV` did not contain
 /// version information and/or the output format underwent breaking changes.
-fn rust_version() -> anyhow::Result<(String, String)> {
+fn rust_llvm_versions() -> anyhow::Result<(String, String)> {
     let cmd = std::env::var("RUSTC").unwrap_or("rustc".into());
     let args = &["-vV"];
 

crates/re_build_tools/src/rebuild_detector.rs

@@ -22,6 +22,7 @@ fn should_run() -> bool {
         // Dependencies shouldn't change on CI, but who knows 🤷‍♂️
         Environment::CI => true,
 
+        // Yes - this is what we want tracking for.
         Environment::DeveloperInWorkspace => true,
 
         // Definitely not
@@ -34,6 +35,9 @@ fn should_run() -> bool {
 ///
 /// This will work even if the package depends on crates that are outside of the workspace,
 /// included with `path = …`
+///
+/// However, this is a complex things, and may have bugs in it.
+/// Maybe it is even causing spurious re-compiles (<https://github.com/rerun-io/rerun/issues/3266>).
 pub fn rebuild_if_crate_changed(pkg_name: &str) {
     if !should_run() {
         return;

crates/re_types/Cargo.toml

@@ -45,6 +45,14 @@ serde = ["dep:serde", "re_string_interner/serde"]
 ## Only useful for testing purposes.
 testing = []
 
+## Special hack!
+##
+## If you configure rust-analyzer to set `--all-features,
+## then this feature will be set and that will ensure that
+## `rust-analyzer` won't run the (expensive) `build.rs`!
+__opt_out_of_auto_rebuild = []
+
+
 [dependencies]
 # Rerun
 re_error.workspace = true