Old syntax suggestion

src/cargo/core/compiler/custom_build.rs

@@ -722,16 +722,35 @@ impl BuildOutput {
  const DOCS_LINK_SUGGESTION: &str = "See https://doc.rust-lang.org/cargo/reference/build-scripts.html#outputs-of-the-build-script \
  for more information about build script outputs.";
 
+ fn has_reserved_prefix(flag: &str) -> bool {
+ RESERVED_PREFIXES
+ .iter()
+ .any(|reserved_prefix| flag.starts_with(reserved_prefix))
+ }
+
  fn check_minimum_supported_rust_version_for_new_syntax(
  pkg_descr: &str,
  msrv: &Option<RustVersion>,
+ flag: &str,
  ) -> CargoResult<()> {
  if let Some(msrv) = msrv {
  let new_syntax_added_in = RustVersion::from_str("1.77.0")?;
  if !new_syntax_added_in.is_compatible_with(msrv.as_partial()) {
+ let old_syntax_suggestion = if has_reserved_prefix(flag) {
+ format!(
+ "Switch to the old `cargo:{flag}` syntax (note the single colon).\n"
+ )
+ } else if flag.starts_with("metadata=") {
+ let old_format_flag = flag.strip_prefix("metadata=").unwrap();
+ format!("Switch to the old `cargo:{old_format_flag}` syntax instead of `cargo::{flag}` (note the single colon).\n")
+ } else {
+ String::new()
+ };
+
  bail!(
  "the `cargo::` syntax for build script output instructions was added in \
  Rust 1.77.0, but the minimum supported Rust version of `{pkg_descr}` is {msrv}.\n\
+ {old_syntax_suggestion}\
  {DOCS_LINK_SUGGESTION}"
  );
  }
@@ -793,16 +812,13 @@ impl BuildOutput {
  };
  let mut old_syntax = false;
  let (key, value) = if let Some(data) = line.strip_prefix("cargo::") {
- check_minimum_supported_rust_version_for_new_syntax(pkg_descr, msrv)?;
+ check_minimum_supported_rust_version_for_new_syntax(pkg_descr, msrv, data)?;
  // For instance, `cargo::rustc-flags=foo` or `cargo::metadata=foo=bar`.
  parse_directive(whence.as_str(), line, data, old_syntax)?
  } else if let Some(data) = line.strip_prefix("cargo:") {
  old_syntax = true;
  // For instance, `cargo:rustc-flags=foo`.
- if RESERVED_PREFIXES
- .iter()
- .any(|prefix| data.starts_with(prefix))
- {
+ if has_reserved_prefix(data) {
  parse_directive(whence.as_str(), line, data, old_syntax)?
  } else {
  // For instance, `cargo:foo=bar`.

tests/testsuite/build_script.rs

@@ -625,7 +625,7 @@ fn custom_build_invalid_host_config_feature_flag() {
  .with_status(101)
  .with_stderr_contains(
  "\
-error: the -Zhost-config flag requires the -Ztarget-applies-to-host flag to be set
+[ERROR] the -Zhost-config flag requires the -Ztarget-applies-to-host flag to be set
 ",
  )
  .run();
@@ -1038,7 +1038,7 @@ fn links_duplicates() {
 
  p.cargo("build").with_status(101)
  .with_stderr("\
-error: failed to select a version for `a-sys`.
+[ERROR] failed to select a version for `a-sys`.
  ... required by package `foo v0.5.0 ([..])`
 versions that meet the requirements `*` are: 0.5.0
 
@@ -1163,7 +1163,7 @@ fn links_duplicates_deep_dependency() {
 
  p.cargo("build").with_status(101)
  .with_stderr("\
-error: failed to select a version for `a-sys`.
+[ERROR] failed to select a version for `a-sys`.
  ... required by package `a v0.5.0 ([..])`
  ... which satisfies path dependency `a` of package `foo v0.5.0 ([..])`
 versions that meet the requirements `*` are: 0.5.0
@@ -4508,7 +4508,7 @@ fn links_duplicates_with_cycle() {
 
  p.cargo("build").with_status(101)
  .with_stderr("\
-error: failed to select a version for `a`.
+[ERROR] failed to select a version for `a`.
  ... required by package `foo v0.5.0 ([..])`
 versions that meet the requirements `*` are: 0.5.0
 
@@ -5315,7 +5315,7 @@ fn wrong_output() {
  .with_stderr(
  "\
 [COMPILING] foo [..]
-error: invalid output in build script of `foo v0.0.1 ([ROOT]/foo)`: `cargo::example`
+[ERROR] invalid output in build script of `foo v0.0.1 ([ROOT]/foo)`: `cargo::example`
 Expected a line with `cargo::KEY=VALUE` with an `=` character, but none was found.
 See https://doc.rust-lang.org/cargo/reference/build-scripts.html#outputs-of-the-build-script \
 for more information about build script outputs.
@@ -5405,7 +5405,7 @@ fn test_invalid_old_syntax() {
  .with_stderr(
  "\
 [COMPILING] foo [..]
-error: invalid output in build script of `foo v0.0.1 ([ROOT]/foo)`: `cargo:foo`
+[ERROR] invalid output in build script of `foo v0.0.1 ([ROOT]/foo)`: `cargo:foo`
 Expected a line with `cargo:KEY=VALUE` with an `=` character, but none was found.
 See https://doc.rust-lang.org/cargo/reference/build-scripts.html#outputs-of-the-build-script \
 for more information about build script outputs.
@@ -5434,7 +5434,7 @@ fn test_invalid_new_syntax() {
  .with_stderr(
  "\
 [COMPILING] foo [..]
-error: invalid output in build script of `foo v0.0.1 ([ROOT]/foo)`: `cargo::metadata=foo`
+[ERROR] invalid output in build script of `foo v0.0.1 ([ROOT]/foo)`: `cargo::metadata=foo`
 Expected a line with `cargo::metadata=KEY=VALUE` with an `=` character, but none was found.
 See https://doc.rust-lang.org/cargo/reference/build-scripts.html#outputs-of-the-build-script \
 for more information about build script outputs.
@@ -5459,7 +5459,7 @@ for more information about build script outputs.
  .with_stderr(
  "\
 [COMPILING] foo [..]
-error: invalid output in build script of `foo v0.0.1 ([ROOT]/foo)`: `cargo::foo=bar`
+[ERROR] invalid output in build script of `foo v0.0.1 ([ROOT]/foo)`: `cargo::foo=bar`
 Unknown key: `foo`.
 See https://doc.rust-lang.org/cargo/reference/build-scripts.html#outputs-of-the-build-script \
 for more information about build script outputs.
@@ -5499,7 +5499,89 @@ fn test_new_syntax_with_old_msrv() {
  .with_stderr_contains(
  "\
 [COMPILING] foo [..]
-error: the `cargo::` syntax for build script output instructions was added in Rust 1.77.0, \
+[ERROR] the `cargo::` syntax for build script output instructions was added in Rust 1.77.0, \
+but the minimum supported Rust version of `foo v0.5.0 ([ROOT]/foo)` is 1.60.0.
+Switch to the old `cargo:foo=bar` syntax instead of `cargo::metadata=foo=bar` (note the single colon).
+See https://doc.rust-lang.org/cargo/reference/build-scripts.html#outputs-of-the-build-script \
+for more information about build script outputs.
+",
+ )
+ .run();
+}
+
+#[cargo_test]
+fn test_new_syntax_with_old_msrv_and_reserved_prefix() {
+ let p = project()
+ .file(
+ "Cargo.toml",
+ r#"
+ [package]
+ name = "foo"
+ version = "0.5.0"
+ edition = "2015"
+ authors = []
+ build = "build.rs"
+ rust-version = "1.60.0"
+ "#,
+ )
+ .file("src/lib.rs", "")
+ .file(
+ "build.rs",
+ r#"
+ fn main() {
+ println!("cargo::rustc-check-cfg=cfg(foo)");
+ }
+ "#,
+ )
+ .build();
+
+ p.cargo("build")
+ .with_status(101)
+ .with_stderr_contains(
+ "\
+[COMPILING] foo [..]
+[ERROR] the `cargo::` syntax for build script output instructions was added in Rust 1.77.0, \
+but the minimum supported Rust version of `foo v0.5.0 ([ROOT]/foo)` is 1.60.0.
+Switch to the old `cargo:rustc-check-cfg=cfg(foo)` syntax (note the single colon).
+See https://doc.rust-lang.org/cargo/reference/build-scripts.html#outputs-of-the-build-script \
+for more information about build script outputs.
+",
+ )
+ .run();
+}
+
+#[cargo_test]
+fn test_new_syntax_with_old_msrv_and_unknown_prefix() {
+ let p = project()
+ .file(
+ "Cargo.toml",
+ r#"
+ [package]
+ name = "foo"
+ version = "0.5.0"
+ edition = "2015"
+ authors = []
+ build = "build.rs"
+ rust-version = "1.60.0"
+ "#,
+ )
+ .file("src/lib.rs", "")
+ .file(
+ "build.rs",
+ r#"
+ fn main() {
+ println!("cargo::foo=bar");
+ }
+ "#,
+ )
+ .build();
+
+ p.cargo("build")
+ .with_status(101)
+ .with_stderr_contains(
+ "\
+[COMPILING] foo [..]
+[ERROR] the `cargo::` syntax for build script output instructions was added in Rust 1.77.0, \
 but the minimum supported Rust version of `foo v0.5.0 ([ROOT]/foo)` is 1.60.0.
 See https://doc.rust-lang.org/cargo/reference/build-scripts.html#outputs-of-the-build-script \
 for more information about build script outputs.