[fud2] update path finding to support multi state input and output (#…

…2134)

This PR begins progress towards addressing #1958. It updates the
algorithm used by `fud2` for finding paths from input files to output
files to take in operations which have many inputs and outputs.

The behavior concurs with the current `fud2` in some but not all cases
and does not maintain `fud2`'s always finding the shortest path of
operations.

Specifying operations themselves and emitting the Ninja file still
assume single state inputs and outputs. This will be changed in further
PRs.

fud2/fud-core/src/cli.rs

@@ -1,5 +1,7 @@
 use crate::config;
-use crate::exec::{Driver, Request, StateRef};
+use crate::exec::{
+    Driver, EnumeratePlanner, Request, SingleOpOutputPlanner, StateRef,
+};
 use crate::run::Run;
 use anyhow::{anyhow, bail};
 use argh::FromArgs;
@@ -91,19 +93,23 @@ struct FakeArgs {
 
     /// the input file
     #[argh(positional)]
-    input: Option<Utf8PathBuf>,
+    input: Vec<Utf8PathBuf>,
 
     /// the output file
     #[argh(option, short = 'o')]
-    output: Option<Utf8PathBuf>,
+    output: Vec<Utf8PathBuf>,
 
-    /// the state to start from
+    /// the states to start from.
+    /// The ith state is applied to the ith input file.
+    /// If more states are specified than files, files for these states are read from stdin.
     #[argh(option)]
-    from: Option<String>,
+    from: Vec<String>,
 
     /// the state to produce
+    /// The ith state is applied to the ith output file.
+    /// If more states are specified than files, files for these states are written to stdout
     #[argh(option)]
-    to: Option<String>,
+    to: Vec<String>,
 
     /// execution mode (run, plan, emit, gen, dot)
     #[argh(option, short = 'm', default = "Mode::Run")]
@@ -132,34 +138,63 @@ struct FakeArgs {
     /// log level for debugging fud internal
     #[argh(option, long = "log", default = "log::LevelFilter::Warn")]
     pub log_level: log::LevelFilter,
+
+    /// use new enumeration algorithm for finding operation sequences
+    #[argh(switch)]
+    planner: bool,
 }
 
-fn from_state(driver: &Driver, args: &FakeArgs) -> anyhow::Result<StateRef> {
-    match &args.from {
-        Some(name) => driver
-            .get_state(name)
-            .ok_or(anyhow!("unknown --from state")),
-        None => match args.input {
-            Some(ref input) => driver
-                .guess_state(input)
-                .ok_or(anyhow!("could not infer input state")),
-            None => bail!("specify an input file or use --from"),
-        },
+fn get_states_with_errors(
+    driver: &Driver,
+    explicit_states: &[String],
+    files: &[Utf8PathBuf],
+    unknown_state: &str,
+    uninferable_file: &str,
+    no_states: &str,
+) -> anyhow::Result<Vec<StateRef>> {
+    let explicit_states = explicit_states.iter().map(|state_str| {
+        driver
+            .get_state(state_str)
+            .ok_or(anyhow!("{unknown_state}"))
+    });
+    let inferred_states =
+        files.iter().skip(explicit_states.len()).map(|input_str| {
+            driver
+                .guess_state(input_str)
+                .ok_or(anyhow!("{uninferable_file}"))
+        });
+    let states = explicit_states
+        .chain(inferred_states)
+        .collect::<Result<Vec<_>, _>>()?;
+    if states.is_empty() {
+        bail!("{no_states}");
     }
+    Ok(states)
 }
 
-fn to_state(driver: &Driver, args: &FakeArgs) -> anyhow::Result<StateRef> {
-    match &args.to {
-        Some(name) => {
-            driver.get_state(name).ok_or(anyhow!("unknown --to state"))
-        }
-        None => match &args.output {
-            Some(out) => driver
-                .guess_state(out)
-                .ok_or(anyhow!("could not infer output state")),
-            None => Err(anyhow!("specify an output file or use --to")),
-        },
-    }
+fn from_states(
+    driver: &Driver,
+    args: &FakeArgs,
+) -> anyhow::Result<Vec<StateRef>> {
+    get_states_with_errors(
+        driver,
+        &args.from,
+        &args.input,
+        "unknown --from state",
+        "could not infer input state",
+        "specify and input file or use --from",
+    )
+}
+
+fn to_state(driver: &Driver, args: &FakeArgs) -> anyhow::Result<Vec<StateRef>> {
+    get_states_with_errors(
+        driver,
+        &args.to,
+        &args.output,
+        "unknown --to state",
+        "could no infer output state",
+        "specify an output file or use --to",
+    )
 }
 
 fn get_request(driver: &Driver, args: &FakeArgs) -> anyhow::Result<Request> {
@@ -185,14 +220,18 @@ fn get_request(driver: &Driver, args: &FakeArgs) -> anyhow::Result<Request> {
                 .ok_or(anyhow!("unknown --through op {}", s))
         })
         .collect();
-
     Ok(Request {
-        start_file: args.input.clone(),
-        start_state: from_state(driver, args)?,
-        end_file: args.output.clone(),
-        end_state: to_state(driver, args)?,
+        start_files: args.input.clone(),
+        start_states: from_states(driver, args)?,
+        end_files: args.output.clone(),
+        end_states: to_state(driver, args)?,
         through: through?,
         workdir,
+        planner: if args.planner {
+            Box::new(EnumeratePlanner {})
+        } else {
+            Box::new(SingleOpOutputPlanner {})
+        },
     })
 }
 

fud2/fud-core/src/exec/data.rs

@@ -24,7 +24,7 @@ impl State {
         self.extensions.iter().any(|e| e == ext)
     }
 
-    /// Is this a "pseudo-state": doesn't correspond to an actual file, and must be an output state?
+    /// Is this a "pseudo-state": doesn't correspond to an actual file
     pub fn is_pseudo(&self) -> bool {
         self.extensions.is_empty()
     }
@@ -38,8 +38,8 @@ entity_impl!(StateRef, "state");
 /// An Operation transforms files from one State to another.
 pub struct Operation {
     pub name: String,
-    pub input: StateRef,
-    pub output: StateRef,
+    pub input: Vec<StateRef>,
+    pub output: Vec<StateRef>,
     pub setups: Vec<SetupRef>,
     pub emit: Box<dyn run::EmitBuild>,
     /// Describes where this operation was defined.