Support --learn for inline expectations via learnEdits

cpp/ql/lib/utils/test/InlineExpectationsTestQuery.ql

@@ -18,4 +18,13 @@ private module Input implements T::TestPostProcessing::InputSig<Impl> {
         f.getRelativePath() + ":" + startline + ":" + startcolumn + ":" + endline + ":" + endcolumn
     )
   }
+
+  bindingset[relativePath]
+  string getStartCommentMarker(string relativePath) {
+    // C/C++ databases can also contain XML (e.g. `.xml`, `.props`), whose block-comment
+    // syntax is not yet supported, so we only render for C/C++ sources.
+    relativePath
+        .regexpMatch(".*\\.(c|cc|cpp|cxx|cp|c\\+\\+|h|hh|hpp|hxx|h\\+\\+|inl|tcc|ipp|tpp|cu|cuh)") and
+    result = "//"
+  }
 }

csharp/ql/lib/utils/test/InlineExpectationsTestQuery.ql

@@ -18,4 +18,12 @@ private module Input implements T::TestPostProcessing::InputSig<Impl> {
         f.getRelativePath() + ":" + startline + ":" + startcolumn + ":" + endline + ":" + endcolumn
     )
   }
+
+  bindingset[relativePath]
+  string getStartCommentMarker(string relativePath) {
+    // C# databases can also contain XML (e.g. `.csproj`, `.config`) and Razor markup, whose
+    // comment syntaxes are not yet supported, so we only render for C# sources.
+    relativePath.regexpMatch(".*\\.(cs|csx)") and
+    result = "//"
+  }
 }

go/ql/lib/utils/test/InlineExpectationsTestQuery.ql

@@ -18,4 +18,12 @@ private module Input implements T::TestPostProcessing::InputSig<Impl> {
         f.getRelativePath() + ":" + startline + ":" + startcolumn + ":" + endline + ":" + endcolumn
     )
   }
+
+  bindingset[relativePath]
+  string getStartCommentMarker(string relativePath) {
+    // Go databases can also contain XML, whose block-comment syntax is not yet supported, so
+    // we only render for Go sources.
+    relativePath.matches("%.go") and
+    result = "//"
+  }
 }

java/ql/lib/utils/test/InlineExpectationsTestQuery.ql

@@ -18,4 +18,12 @@ private module Input implements T::TestPostProcessing::InputSig<Impl> {
         f.getRelativePath() + ":" + startline + ":" + startcolumn + ":" + endline + ":" + endcolumn
     )
   }
+
+  bindingset[relativePath]
+  string getStartCommentMarker(string relativePath) {
+    // Java databases can also contain XML; those files use a different (block) comment
+    // syntax that is not yet supported, so we only render for Java and Kotlin sources.
+    (relativePath.matches("%.java") or relativePath.matches("%.kt")) and
+    result = "//"
+  }
 }

javascript/ql/lib/utils/test/InlineExpectationsTestQuery.ql

@@ -18,4 +18,12 @@ private module Input implements T::TestPostProcessing::InputSig<Impl> {
         f.getRelativePath() + ":" + startline + ":" + startcolumn + ":" + endline + ":" + endcolumn
     )
   }
+
+  bindingset[relativePath]
+  string getStartCommentMarker(string relativePath) {
+    // JavaScript databases can also contain HTML, whose (block) comment syntax is not yet
+    // supported, so we only render for the line-comment source files.
+    relativePath.regexpMatch(".*\\.(js|cjs|mjs|jsx|ts|cts|mts|tsx)") and
+    result = "//"
+  }
 }

python/ql/lib/utils/test/InlineExpectationsTestQuery.ql

@@ -18,4 +18,12 @@ private module Input implements T::TestPostProcessing::InputSig<Impl> {
         f.getRelativePath() + ":" + startline + ":" + startcolumn + ":" + endline + ":" + endcolumn
     )
   }
+
+  bindingset[relativePath]
+  string getStartCommentMarker(string relativePath) {
+    // Python databases can also contain XML, whose block-comment syntax is not yet supported,
+    // so we only render for Python sources.
+    relativePath.regexpMatch(".*\\.(py|pyi)") and
+    result = "#"
+  }
 }

ql/ql/src/utils/test/InlineExpectationsTestQuery.ql

@@ -18,4 +18,12 @@ private module Input implements T::TestPostProcessing::InputSig<Impl> {
         f.getRelativePath() + ":" + startline + ":" + startcolumn + ":" + endline + ":" + endcolumn
     )
   }
+
+  bindingset[relativePath]
+  string getStartCommentMarker(string relativePath) {
+    // The QL extractor can also extract YAML (e.g. `qlpack.yml`), whose `#` comment syntax
+    // differs, so we only render for QL sources and dbscheme files.
+    relativePath.regexpMatch(".*\\.(ql|qll|dbscheme)") and
+    result = "//"
+  }
 }

ruby/ql/lib/utils/test/InlineExpectationsTestQuery.ql

@@ -18,4 +18,12 @@ private module Input implements T::TestPostProcessing::InputSig<Impl> {
         f.getRelativePath() + ":" + startline + ":" + startcolumn + ":" + endline + ":" + endcolumn
     )
   }
+
+  bindingset[relativePath]
+  string getStartCommentMarker(string relativePath) {
+    // Ruby databases can also contain ERB, whose comment syntax is not yet supported, so we
+    // only render for plain Ruby sources.
+    relativePath.matches("%.rb") and
+    result = "#"
+  }
 }

rust/ql/lib/utils/test/InlineExpectationsTestQuery.ql

@@ -18,4 +18,12 @@ private module Input implements T::TestPostProcessing::InputSig<Impl> {
         f.getRelativePath() + ":" + startline + ":" + startcolumn + ":" + endline + ":" + endcolumn
     )
   }
+
+  bindingset[relativePath]
+  string getStartCommentMarker(string relativePath) {
+    // Rust databases can also contain YAML, whose `#` comment syntax differs, so we only
+    // render for Rust sources.
+    relativePath.matches("%.rs") and
+    result = "//"
+  }
 }

shared/util/codeql/util/test/InlineExpectationsTest.qll

@@ -635,6 +635,28 @@ module TestPostProcessing {
 
   signature module InputSig<InlineExpectationsTestSig Input> {
     string getRelativeUrl(Input::Location location);
+
+    /**
+     * Gets the marker that starts a line comment (for example `"//"` or `"#"`) in the source
+     * file with the given `relativePath`, provided that `codeql test run --learn` is able to
+     * render inline expectations for that file. Files for which this has no result are left
+     * untouched by `--learn`.
+     *
+     * This is keyed on the file rather than on the analyzed language because a single database
+     * may contain source files in several languages with different comment syntaxes (for
+     * example Java together with XML). `relativePath` is the path reported by `getRelativeUrl`.
+     */
+    bindingset[relativePath]
+    string getStartCommentMarker(string relativePath);
+
+    /**
+     * Gets the marker that ends a comment (for example `"-->"`) in the source file with the
+     * given `relativePath`. Defaults to the empty string, which is correct for languages whose
+     * inline expectations use line comments; block-comment languages can override it so that
+     * `--learn` renders a closing marker.
+     */
+    bindingset[relativePath]
+    default string getEndCommentMarker(string relativePath) { result = "" }
   }
 
   module Make<InlineExpectationsTestSig Input, InputSig<Input> Input2> {
@@ -1011,5 +1033,105 @@ module TestPostProcessing {
       Test::testFailures(_, _) and
       relation = "testFailures"
     }
+
+    /**
+     * Gets the fully rendered inline expectation comment (including the comment markers) that
+     * `--learn` should insert for a new `tag` expectation in the file with the given
+     * `relativePath`, or has no result if that file's comment syntax is not supported.
+     *
+     * The leading space separates the comment from any existing content on the line.
+     */
+    bindingset[relativePath, tag]
+    private string renderExpectationComment(string relativePath, string tag) {
+      exists(string startMarker, string endMarker, string endSuffix |
+        startMarker = Input2::getStartCommentMarker(relativePath) and
+        endMarker = Input2::getEndCommentMarker(relativePath) and
+        (
+          endMarker = "" and endSuffix = ""
+          or
+          endMarker != "" and endSuffix = " " + endMarker
+        ) and
+        result = " " + startMarker + " $ " + tag + endSuffix
+      )
+    }
+
+    /**
+     * Holds if `codeql test run --learn` should edit the source file `file` so that its inline
+     * expectations match the current query results. Each row asks the test runner to change
+     * `line`, where `operation` is either:
+     *
+     * - `"append"`: add `text` (a fully rendered comment) at the end of the line; `startColumn`
+     *   and `endColumn` are both 0.
+     * - `"replace"`: replace the 1-based inclusive column range `[startColumn, endColumn]` with
+     *   `text` (the empty string deletes the range).
+     *
+     * Only a deliberately reliable subset is emitted so far, restricted to the plain `Alert`
+     * tag with no value or query-id annotation:
+     *
+     * - an actual result with no matching expectation gets a new `// $ Alert` comment appended
+     *   (an *unexpected result*), and
+     * - a plain `// $ Alert` comment whose result is now missing, and which is the only
+     *   expectation on that comment, is removed (a *missing result*).
+     *
+     * Cases that need sub-comment column information (promoting `MISSING:`/clearing `SPURIOUS:`,
+     * or editing one tag among several on a line) are intentionally left for a follow-up.
+     */
+    query predicate learnEdits(
+      string file, int line, string operation, int startColumn, int endColumn, string text
+    ) {
+      // Unexpected result: append a new `// $ Alert` comment on the alert's line. The comment
+      // must go on the result's *end* line, because an expectation matches a result when the
+      // expectation's start line equals the result's end line (see `onSameLine`). For most
+      // languages a result spans a single line, but some (e.g. Rust) include leading trivia in
+      // the location, so the start and end lines differ.
+      exists(Test::ActualTestResult actualResult, string relativePath, int el, string comment |
+        actualResult.getTag() = "Alert" and
+        actualResult.getValue() = "" and
+        not actualResult.isOptional() and
+        not exists(
+          Test::getAMatchingExpectation(actualResult.getLocation(), actualResult.toString(),
+            actualResult.getTag(), actualResult.getValue(), false)
+        ) and
+        parseLocationString(actualResult.getLocation().getRelativeUrl(), relativePath, _, _, el, _) and
+        comment = renderExpectationComment(relativePath, "Alert") and
+        file = relativePath and
+        line = el and
+        operation = "append" and
+        startColumn = 0 and
+        endColumn = 0 and
+        text = comment
+      )
+      or
+      // Missing result: remove a plain `// $ Alert` comment that is the comment's sole
+      // expectation and no longer matches any actual result.
+      exists(Test::GoodTestExpectation expectation, string relativePath, int sl, int sc |
+        expectation.getTag() = "Alert" and
+        expectation.getValue() = "" and
+        not expectation = Test::getAMatchingExpectation(_, _, _, _, _) and
+        // the comment carries exactly this one expectation, so removing it wholesale is safe
+        count(Test::FailureLocatable other |
+          other.getLocation() = expectation.getLocation() and
+          (
+            other instanceof Test::GoodTestExpectation or
+            other instanceof Test::FalsePositiveTestExpectation or
+            other instanceof Test::FalseNegativeTestExpectation
+          )
+        ) = 1 and
+        not exists(Test::InvalidTestExpectation invalid |
+          invalid.getLocation() = expectation.getLocation()
+        ) and
+        parseLocationString(expectation.getLocation().getRelativeUrl(), relativePath, sl, sc, _, _) and
+        file = relativePath and
+        line = sl and
+        operation = "replace" and
+        startColumn = sc and
+        // A trailing inline expectation comment always runs to the end of its line, so delete from
+        // the comment marker to the end of the line. `endColumn = 0` is the engine's "to end of
+        // line" convention; using it avoids depending on how each extractor reports a line
+        // comment's end column (e.g. Swift reports it as ending at column 1 of the next line).
+        endColumn = 0 and
+        text = ""
+      )
+    }
   }
 }

swift/ql/lib/utils/test/InlineExpectationsTestQuery.ql

@@ -18,4 +18,11 @@ private module Input implements T::TestPostProcessing::InputSig<Impl> {
         f.getRelativePath() + ":" + startline + ":" + startcolumn + ":" + endline + ":" + endcolumn
     )
   }
+
+  bindingset[relativePath]
+  string getStartCommentMarker(string relativePath) {
+    // The Swift extractor only ingests Swift sources (no XML/YAML/HTML in its dbscheme), so a
+    // constant marker is safe; revisit if Swift ever gains extraction of another file type.
+    exists(relativePath) and result = "//"
+  }
 }

unified/ql/lib/utils/test/InlineExpectationsTestQuery.ql

@@ -18,4 +18,14 @@ private module Input implements T::TestPostProcessing::InputSig<Impl> {
         f.getRelativePath() + ":" + startline + ":" + startcolumn + ":" + endline + ":" + endcolumn
     )
   }
+
+  bindingset[relativePath]
+  string getStartCommentMarker(string relativePath) {
+    // The unified extractor is a new tree-sitter-based extractor that currently ingests only
+    // Swift sources (see `file_types` in its `codeql-extractor.yml`), which use `//`. Gating on
+    // the extension keeps this correct if it later gains a language with a different comment
+    // syntax.
+    relativePath.regexpMatch(".*\\.(swift|swiftinterface)") and
+    result = "//"
+  }
 }