make: Fix intermittent dash_r_with_file test failure and inference ru…

make/src/lib.rs

@@ -39,7 +39,12 @@ const DEFAULT_SHELL: &str = "/bin/sh";
 /// The only way to create a Make is from a Makefile and a Config.
 pub struct Make {
     macros: Vec<VariableDefinition>,
+    /// Target rules (non-special, non-inference).
+    /// Invariant: inference rules are never stored here, so `first_target()`
+    /// always returns a valid default target per POSIX.
     rules: Vec<Rule>,
+    /// Inference rules (e.g. `.c.o:`, `.txt.out:`).
+    inference_rules: Vec<Rule>,
     default_rule: Option<Rule>, // .DEFAULT
     pub config: Config,
 }
@@ -58,25 +63,84 @@ impl Make {
     }
 
     pub fn first_target(&self) -> Result<&Target, ErrorCode> {
-        let rule = self.rules.first().ok_or(NoTarget { target: None })?;
+        // Per POSIX: "the first target that make encounters that is not a special
+        // target or an inference rule shall be used."
+        // If there are no non-special, non-inference targets, fall back to the
+        // first inference rule (which will scan CWD for matching files).
+        let rule = self
+            .rules
+            .first()
+            .or_else(|| self.inference_rules.first())
+            .ok_or(NoTarget { target: None })?;
         rule.targets().next().ok_or(NoTarget { target: None })
     }
 
+    /// Finds a matching inference rule for the given target name.
+    ///
+    /// Per POSIX: the suffix of the target (.s1) is compared to .SUFFIXES.
+    /// If found, inference rules are searched for the first .s2.s1 rule whose
+    /// prerequisite file ($*.s2) exists.
+    fn find_inference_rule(&self, name: &str) -> Option<&Rule> {
+        let suffixes = self.config.rules.get(".SUFFIXES")?;
+
+        // Find the target's suffix (.s1)
+        let target_suffix = suffixes
+            .iter()
+            .filter(|s| name.ends_with(s.as_str()))
+            .max_by_key(|s| s.len())?;
+
+        let stem = &name[..name.len() - target_suffix.len()];
+
+        // Search inference rules for .s2.s1 where $*.s2 exists
+        for rule in &self.inference_rules {
+            let Some(rule_target) = rule.targets().next() else {
+                continue;
+            };
+            if let Target::Inference { from, to, .. } = rule_target {
+                let expected_suffix = format!(".{}", to);
+                if expected_suffix == *target_suffix {
+                    let prereq_path = format!("{}.{}", stem, from);
+                    if std::path::Path::new(&prereq_path).exists() {
+                        return Some(rule);
+                    }
+                }
+            }
+        }
+        None
+    }
+
     /// Builds the target with the given name.
     ///
     /// # Returns
     /// - Ok(true) if the target was built.
     /// - Ok(false) if the target was already up to date.
     /// - Err(_) if any errors occur.
     pub fn build_target(&self, name: impl AsRef<str>) -> Result<bool, ErrorCode> {
+        // Search both regular rules and inference rules
         let rule = match self.rule_by_target_name(&name) {
             Some(rule) => rule,
-            None => match &self.default_rule {
+            None => match self
+                .inference_rules
+                .iter()
+                .find(|rule| rule.targets().any(|t| t.as_ref() == name.as_ref()))
+            {
                 Some(rule) => rule,
                 None => {
-                    return Err(NoTarget {
-                        target: Some(name.as_ref().to_string()),
-                    })
+                    // Per POSIX: "If a target exists and there is neither a target rule
+                    // nor an inference rule for the target, the target shall be considered
+                    // up-to-date."
+                    if get_modified_time(&name).is_some() {
+                        return Ok(false);
+                    }
+                    // No rule and file doesn't exist - try .DEFAULT or fail
+                    match &self.default_rule {
+                        Some(rule) => rule,
+                        None => {
+                            return Err(NoTarget {
+                                target: Some(name.as_ref().to_string()),
+                            })
+                        }
+                    }
                 }
             },
         };
@@ -111,6 +175,18 @@ impl Make {
         for prerequisite in &newer_prerequisites {
             self.build_target(prerequisite)?;
         }
+
+        // Per POSIX: "When no target rule with commands is found to update a
+        // target, the inference rules shall be checked."  If the matched target
+        // rule has no recipes, look for a matching inference rule and run it
+        // for this specific target instead.
+        if rule.recipes().count() == 0 {
+            if let Some(inference_rule) = self.find_inference_rule(target.as_ref()) {
+                inference_rule.run_for_target(&self.config, &self.macros, target, up_to_date)?;
+                return Ok(true);
+            }
+        }
+
         rule.run(&self.config, &self.macros, target, up_to_date)?;
 
         Ok(true)
@@ -184,32 +260,60 @@ impl TryFrom<(Makefile, Config)> for Make {
     type Error = ErrorCode;
 
     fn try_from((makefile, config): (Makefile, Config)) -> Result<Self, Self::Error> {
-        let mut rules = vec![];
-        let mut special_rules = vec![];
-        let mut inference_rules = vec![];
-
-        for rule in makefile.rules() {
-            let rule = Rule::from(rule);
+        // Two-pass classification: .SUFFIXES must be processed before inference
+        // rule classification so that user-defined suffixes (especially with -r)
+        // are available when determining whether a rule like `.txt.out:` is an
+        // inference rule.
+
+        let mut suffixes_rules = vec![];
+        let mut remaining_parsed_rules = vec![];
+
+        // Pass 1: Separate .SUFFIXES rules from everything else and process
+        // them immediately so config.rules[".SUFFIXES"] is populated.
+        for parsed_rule in makefile.rules() {
+            let rule = Rule::from(parsed_rule);
             let Some(target) = rule.targets().next() else {
                 return Err(NoTarget { target: None });
             };
-
-            if SpecialTarget::try_from(target.clone()).is_ok() {
-                special_rules.push(rule);
-            } else if InferenceTarget::try_from((target.clone(), config.clone())).is_ok() {
-                inference_rules.push(rule);
+            if let Ok(SpecialTarget::Suffixes) = SpecialTarget::try_from(target.clone()) {
+                suffixes_rules.push(rule);
             } else {
-                rules.push(rule);
+                remaining_parsed_rules.push(rule);
             }
         }
 
+        // Build the Make struct early so we can process .SUFFIXES via the
+        // normal special_target::process path (which writes to make.config).
         let mut make = Self {
-            rules,
+            rules: vec![],
+            inference_rules: vec![],
             macros: makefile.variable_definitions().collect(),
             default_rule: None,
             config,
         };
 
+        for rule in suffixes_rules {
+            special_target::process(rule, &mut make)?;
+        }
+
+        // Pass 2: Classify remaining rules.  Now make.config.rules[".SUFFIXES"]
+        // contains both built-in (unless -r) and user-defined suffixes.
+        let mut special_rules = vec![];
+
+        for rule in remaining_parsed_rules {
+            let Some(target) = rule.targets().next() else {
+                return Err(NoTarget { target: None });
+            };
+
+            if SpecialTarget::try_from(target.clone()).is_ok() {
+                special_rules.push(rule);
+            } else if InferenceTarget::try_from((target.clone(), make.config.clone())).is_ok() {
+                make.inference_rules.push(rule);
+            } else {
+                make.rules.push(rule);
+            }
+        }
+
         for rule in special_rules {
             special_target::process(rule, &mut make)?;
         }

make/src/rule.rs

@@ -66,6 +66,37 @@ impl Rule {
         self.recipes.iter()
     }
 
+    /// Runs an inference rule for a specific target (not a CWD scan).
+    ///
+    /// This is used when POSIX requires applying an inference rule to a specific
+    /// target that has no commands of its own. The internal macros ($<, $*, etc.)
+    /// are substituted based on the target name and the inference rule's suffixes.
+    pub fn run_for_target(
+        &self,
+        global_config: &GlobalConfig,
+        macros: &[VariableDefinition],
+        target: &Target,
+        up_to_date: bool,
+    ) -> Result<(), ErrorCode> {
+        // For an inference rule applied to a specific target, compute the
+        // input/output pair from the target name and the rule's suffixes.
+        let files = if let Some(Target::Inference { from, to, .. }) = self.targets().next() {
+            let target_name = target.as_ref();
+            let expected_suffix = format!(".{}", to);
+            if let Some(stem) = target_name.strip_suffix(&expected_suffix) {
+                let input = PathBuf::from(format!("{}.{}", stem, from));
+                let output = PathBuf::from(target_name);
+                vec![(input, output)]
+            } else {
+                vec![(PathBuf::from(""), PathBuf::from(""))]
+            }
+        } else {
+            vec![(PathBuf::from(""), PathBuf::from(""))]
+        };
+
+        self.run_with_files(global_config, macros, target, up_to_date, files)
+    }
+
     /// Runs the rule with the global config and macros passed in.
     ///
     /// Returns `Ok` on success and `Err` on any errors while running the rule.
@@ -75,6 +106,32 @@ impl Rule {
         macros: &[VariableDefinition],
         target: &Target,
         up_to_date: bool,
+    ) -> Result<(), ErrorCode> {
+        let files = match target {
+            Target::Inference { from, to, .. } => find_files_with_extension(from)?
+                .into_iter()
+                .map(|input| {
+                    let mut output = input.clone();
+                    output.set_extension(to);
+                    (input, output)
+                })
+                .collect::<Vec<_>>(),
+            _ => {
+                vec![(PathBuf::from(""), PathBuf::from(""))]
+            }
+        };
+
+        self.run_with_files(global_config, macros, target, up_to_date, files)
+    }
+
+    /// Internal helper: runs the rule's recipes for the given input/output file pairs.
+    fn run_with_files(
+        &self,
+        global_config: &GlobalConfig,
+        macros: &[VariableDefinition],
+        target: &Target,
+        up_to_date: bool,
+        files: Vec<(PathBuf, PathBuf)>,
     ) -> Result<(), ErrorCode> {
         let GlobalConfig {
             ignore: global_ignore,
@@ -97,20 +154,6 @@ impl Rule {
             phony: _,
         } = self.config;
 
-        let files = match target {
-            Target::Inference { from, to, .. } => find_files_with_extension(from)?
-                .into_iter()
-                .map(|input| {
-                    let mut output = input.clone();
-                    output.set_extension(to);
-                    (input, output)
-                })
-                .collect::<Vec<_>>(),
-            _ => {
-                vec![(PathBuf::from(""), PathBuf::from(""))]
-            }
-        };
-
         for inout in files {
             for recipe in self.recipes() {
                 let RecipeConfig {

make/src/special_target.rs

@@ -200,6 +200,7 @@ impl Processor<'_> {
             self.make
                 .rules
                 .iter_mut()
+                .chain(self.make.inference_rules.iter_mut())
                 .filter(|r| r.targets().any(|t| t.as_ref() == prerequisite.as_ref()))
                 .for_each(f.clone());
         }
@@ -209,7 +210,11 @@ impl Processor<'_> {
     ///   specified.
     fn global(&mut self, f: impl FnMut(&mut Rule) + Clone) {
         if self.rule.prerequisites().count() == 0 {
-            self.make.rules.iter_mut().for_each(f);
+            self.make
+                .rules
+                .iter_mut()
+                .chain(self.make.inference_rules.iter_mut())
+                .for_each(f);
         }
     }
 }